Significant Modification of Pairwisecontinuous
Functions with Associated Concepts
ALI A. ATOOM1, HAMZA QOQAZEH2, RAHMEH ALRABABAH1, EMAN ALMUHUR3,
NABEELA ABU-ALKISHIK4
1Department of Mathematics, Faculty of Science,
Ajloun National University,
P.O. Box 43, Ajloun, 26810,
JORDAN
2Department of Mathematics, Faculty of Arts and Science,
Amman Arab University,
P.O. Box 24 Amman, 11953,
JORDAN
3Department of Mathematics, Faculty of Science,
Ajloun National University
P.O. Box 43, Ajloun, 26810,
JORDAN
4Department of Mathematics, Faculty of Science
Jerash University
P.O. Box 2600, Jerash, 21220
JORDAN
Abstract: - The continuity is generalized by the notion of continuous functions. In this research, we present
a new weaker form for continuous functions called pairwise continuous functions. Additionally, we define
pairwise barely continuous functions, a new, weaker form of barely continuous functions. We study
the basic characteristics and impacts of pairwise continuous functions, clarifying their connection with
typical continuity and providing perspectives on the wider field of topological analysis. It explores related ideas
like the limit, which describes how sequences behave over certain conditions when the function is applied.
In addition, the concepts highlight the importance of pairwise continuous functions in theoretical and
practical conditions by discussing their relationships with other functional structures. An extensive number of
demonstrative examples will be presented, along with the new results and theorems about pairwise barely
continuous and pairwise continuous functions that generalize.
Key-Words: - Bitopological spaces, pairclosed, pairlindelöf, pair contiuous, pairalmost con-
tenuous functions, pairweakly continuous functions, pairsequentially continuous functions,
pairbarely continuous functions, pairbarely continuous functions.
Received: March 26, 2023. Revised: November 19, 2023. Accepted: December 9, 2023. Published: December 31, 2023.
1 Introduction
Pairwise-ω-continuous function analysis is seen as
an extension of a similar topic in topological spaces,
whose was a development of topological spaces
with simply one topology.
The primary goal for including ω-continuous
functions in the topology is to generalize certain
characteristics of continuous functions. In generic
topology, compactness and lindelöf are the most
basic components. Moreover, these two concepts
have a great deal of utility in implementations;
topology is employed in various fields of analysis as
well as logical mathematics, and continuous
function conceptions are utilized widely in
mathematical analysis. Since in, [1], first proposed
the idea of a bitopological space in 1963, certain
topological properties of single topology such as
compactness and paracompactness have been
WSEAS TRANSACTIONS on MATHEMATICS
DOI: 10.37394/23206.2023.22.105
Ali A. Atoom, Hamza Qoqazeh,
Rahmeh Alrababah, Eman Almuhur,
Nabeela Abu-Alkishik
E-ISSN: 2224-2880
961
Volume 22, 2023
generalised to bitopological spaces, as well as
separation axioms, connectedness, function types,
and more concepts. In 1982, [2], demonstrated that
the lindelöf property is maintained by counter
images of closed mappings using lindelöf
counter images for points. He introduced a new type
of mapping, called closed mappings, that are
strictly weaker than closed mappings. Also, he
demonstrated that if the inverse image of every
point in the range is paracompact with respect to the
domain (lindelöf, respectively), then the
paracompactness (strongly paracompactness)
property is maintained by obtaining counter images
of closed mappings using regular domains.
Moreover, he defined space as a generalisation
of space and demonstrated that for any
space , the projection of   is
closed if and only if is in a lindelöf space.
Additionally, he derived various product theorems
related to lindelöf for paracompact and strongly
paracompact spaces using spaces. He then
discusses a few different examples that relate to the
definitions and theorems that are provided. In 2021,
in, [3], introduces pairwise perfect functions as
well as pairwise perfect functions,
describing their features and searching for
homeomorphisms between various bitopological
spaces under their influence. Finally, he provides
the product theorem characterizations. In 2022, [4],
presented the idea of weakly continuous
functions within bitopological spaces as a
generalisation of continuous functions, and
they obtained numerous features and some of their
characteristics. Also, in the same year 2022, [5],
proposed the idea of nearly continuous
functions within bitopological spaces as a
generalization of continuous functions, and
they established several results and some of their
characteristics. While, in 2022, [6], created a new
type of function via open sets that he named
rarely continuous function and examined many
characteristics of this function. Throughout this
research, we will use paircompact, which refers to
pairwise compact and pair to denotes pairwise. If
󰇛󰇜represents a bitopological space and 
; then the closure for with regard to and ,
respectively, will be indicated by the symbols
󰇛󰇜 and 󰇛󰇜. Let be a subset of and let
󰇛󰇜 be any topological space, a point
󰇛󰇜is known as the condensation point of
if is uncountable set, for any with
. The following describes the way, [7], described
closed sets as well as open sets. If A has all
its condensation points, it is said to as closed.
open is the complement of a closed set.
Additionally, the intersection with all closed
sets that contain will be indicated by 󰇛󰇜.
Also, the space 󰇛󰇜, or just refers to any
bitopological space on which, unless otherwise
specified, no separation axioms can be taken for
assumed in this resaerch. Paircontinuous
functions are a new kind of weakened continuous
function that is introduced in this study.
Additionally, we define pairbarely continuous
functions, a new, weakened type of barely
continuous functions. First, in Section 3, we
establish numerous characteristics of
paircontinuous functions. Several examples
are provided in Section 4 to show how
paircontinuous functions and certain
weakened forms of pairwise continuous functions
are connected. In the end, we show whether a
pairω-continuous image that represents a
pairlindelöf space is also a pairlindelöf space in
Section 5 by presenting a new, basic
characterization of pairlindelöf spaces.
Furthermore, as demonstrated in Section 5, a
pairwise only barely continuous image is
hereditarily. Applications of continuous functions
with different topological spaces can be found in
[8], [9], [10], [11], [12], [13], [14], [15], [16], [17],
[18], [19], [20], [21], [22], [23], [24], [25], [26],
[27], [28], [29].
2 Preliminaries
This section presents some significant concepts
along with specifics are covered that used within the
research.
Definition 2.1, [2] A function 󰇛󰇜
󰇛󰇜 is said to be paircontinuous if the
functions 󰇛󰇜󰇛󰇜 and 󰇛󰇜
󰇛󰇜 are continuous.
Definition 2.2, [2] A function 󰇛󰇜
󰇛󰇜 is said to be pairclosed if the functions
󰇛󰇜󰇛󰇜 and 󰇛󰇜󰇛󰇜 are
closed.
Definition 2.3, [2] Let 󰇛󰇜 be any
bitopological space. Then, a cover of the space
󰇛󰇜 is called open if  .
Moreover, is called pairopen if has at least
one-nonempty member of .
Definition 2.4, [2] Let 󰇛󰇜 be any
bitopological space. Then, the space is called
WSEAS TRANSACTIONS on MATHEMATICS
DOI: 10.37394/23206.2023.22.105
Ali A. Atoom, Hamza Qoqazeh,
Rahmeh Alrababah, Eman Almuhur,
Nabeela Abu-Alkishik
E-ISSN: 2224-2880
962
Volume 22, 2023
pairlindelöf if any pairopen cover of 󰇛󰇜
has a countable subcover.
Definition 2.5, [2] Let 󰇛󰇜 be any
bitopological space. Then, the space is called
lindelöf if any open cover of 󰇛󰇜
has a countable subcover.
Definition 2.6, [2] Let 󰇛󰇜 be any
bitopological space. Then, the space is called
paircountably compact if any countable pairopen
cover of 󰇛󰇜 has a finite subcover.
Definition 2.7, [2] Let 󰇛󰇜 be any
bitopological space. Then, the space is called
semicountably compact if any countably
open cover of 󰇛󰇜 has a finite
subcover.
Definition 2.8, [2] A function 󰇛󰇜
󰇛󰇜 is said to be pairlindelöf if for any
pairlindelöf closed subset of the space
󰇛󰇜, 󰇛󰇜 is pairlindelöf.
Definition 2.9, [10] A function 󰇛󰇜
󰇛󰇜 is said to be semilindelöf if for any
semilindelöf closed subset of the space
󰇛󰇜, 󰇛󰇜 is semilindelöf.
Definition 2.10, [10] Let 󰇛󰇜 be any
bitopological space, then we called represents
locally lindelöf with a respect to , if there exists
nbd of for any 󰇛󰇜, such that
is pairlindelöf.
Definition 2.11, [10] Let 󰇛󰇜 be any
bitopological space, then the space called
pairlocally lindelöf if and only if is locally
lindelöf with respect to , where  and
.
Definition 2.12, [22] A function 󰇛󰇜
󰇛󰇜 is said to be pairclosed if the
functions represent pairclosed sets onto
pairclosed sets.
Definition 2.13, [24] A function 󰇛󰇜
󰇛󰇜 is called pairweakly continuous if for
any pairopen set  , there is 󰇛󰇜 is
pairopen.
Definition 2.14, [25] A function 󰇛󰇜
󰇛󰇜 is called pairalmost continuous if for
any and any open set of containing
󰇛󰇜 there exists open set containing such
that 󰇛󰇜 󰇛󰇛󰇜󰇜.
Definition 2.15, [25] A function 󰇛󰇜
󰇛󰇜 is called pairweakly continuous if for
any and any open set of containing
󰇛󰇜 there exists open set containing such
that 󰇛󰇜 .
Recall that if an arbitrary neighbourhood (in
simply nbd) for a point in a space includes an
uncountable subset of the set  , then the point
is known as a condensation point of a set .
Definition 2.16, [29] Let 󰇛󰇜 be any
bitopological space and . The space is said to
be pairopen if for any there is a
pairopen subset of containing such that the
set is countable. Moreover, the complement
set of pairopen is called pair closed set.
The family of all pairopen (respectively
pairclosed) subsets of 󰇛󰇜 is
represented as pair󰇛󰇜,(respectively
pair󰇛󰇜). Additionally, the family of all
pairopen of the space 󰇛󰇜 containing
is represented as pair󰇛󰇜.
Definition 2.17, [29] Let 󰇛󰇜 be any
bitopological space and . The space is said to
be semiopen if for any there exists
open subset of containing such that the
set is countable. Moreover, the complement
set of semi open is called semiclosed set.
The family of all semiopen (respectively
semiclosed) subsets of 󰇛󰇜 is
represented as semi󰇛󰇜 (respectively
semi󰇛󰇜). Additionally, the family of all
semiopen of the space 󰇛󰇜 containing
is represented as semi󰇛󰇜.
Definition 2.18, [29] A function 󰇛󰇜
󰇛󰇜 is said to be semiclosed if the
functions represent semiclosed sets onto
semiclosed sets.
Theorem 2.19, [29] 󰇛󰇜 Every pair subset of
the pairlindelöf space is pairlindelöf.
󰇛󰇜 Let function 󰇛󰇜󰇛󰇜 be
any pairfunction. Then the following facts are
equivalent: (a) is pair closed; (b) for any
󰇛󰇜 and each pairopen set , where
󰇛󰇜 , there exists pairopen set
such that and 󰇛󰇜 .
WSEAS TRANSACTIONS on MATHEMATICS
DOI: 10.37394/23206.2023.22.105
Ali A. Atoom, Hamza Qoqazeh,
Rahmeh Alrababah, Eman Almuhur,
Nabeela Abu-Alkishik
E-ISSN: 2224-2880
963
Volume 22, 2023
(iii) Every pairlindelöf, pairopen subset of
󰇛󰇜 represent , which is pairopen
and is countable set such that is set.
3 Properties of Pairwise -Continuous
Functions
Additional results regarding the topological
attributes of pairwise-ω-continuous functions are
presented in this section. Following this, we will
talk about the idea of pairwise-ω-continuous
functions, extract some of their traits, and explain
how they relate to various kinds of pairwise-ω-
continuous functions, providing examples to
demonstrate for every instance. There will also be
discussion and proof of other theories on this topic.
Definition 3.1 A function 󰇛󰇜
󰇛󰇜 is said to be pair continuous at the
point 󰇛󰇜, if for any pair-open set
containing 󰇛󰇜, there is pairopen set
containing such that 󰇛󰇜 . Moreover, a
function is called paircontinuous on
󰇛󰇜, if the function is paircontinuous
at any point of 󰇛󰇜.
The subsequent pair of instances demonstrates
that pairwise-ω-continuous functions at a specific
point are not always pairwise almost continuous at
the identical place, and pairwise almost continuous
functions at a particular point are not always
pairwise ω-continuous at the identical location.
Example 3.2
Let the set represents the real numbers and let
is the usual topology on . Providing the function
󰇛󰇜󰇛󰇜 , which is defined as
(z)=0, in the case of a z is rational, and (z)=1,
in the case of a z is irrational. Therefore at each
irrational number, ψ is pairwise-ω-continuous; at
every single real number, nevertheless, ψ is not
pairwise almost continuous.
Example 3.3
Let the set represents the real numbers and let
is the usual topology on . Consider 󰇝󰇞,
with the topology 󰇝󰇝󰇞. Consider
󰇛󰇜󰇛󰇜, which is defined as
(z)=a, in the case of a z is rational, and (z)=b, in
the case of a z is irrational. nevertheless, ψ is
pairwise almost continuous at every rational
number, nevertheless, ψ is not pairwise-ω-
continuous.
Any paircontinuous function is obviously
paircontinuous. The example that follows,
nevertheless, demonstrates that this need not be
necessary.
Example 3.4 Let be any topology on where n
neighborhoods of every nonzero point are as in the
form of usual topology, whereas n neighborhoods of
will represent as , with is a neighborhoods
of in the usual topology and 󰇥
󰇦. Now, let be a usual topology on . Let
the identity function be denoted by 󰇛󰇜
󰇛󰇜. Then, while is clearly paircontinuous,
it cannot be paircontinuous at as a result.
Note that if 󰇛󰇜 represents a bitopological
space, then the family of every one of open sets
represent a topology , which is finer than .
Therefore, 󰇛󰇜󰇛󰇜 is pair-ω-
continuous if and only if 󰇛󰇜
󰇛󰇜 is paircontinuous. The next theorems
are then stated with simplicity.
Theorem 3.5 Let 󰇛󰇜󰇛󰇜 be a
function. Then we have the equivalent statements as
follows:
(1) the function is pair continuous,
(2) the function 󰇛󰇜󰇛󰇜 is
paircontinuous,
(3) for any pairopen set of 󰇛󰇜, 󰇛󰇜
is pairopen set in 󰇛󰇜.
(4) for any pairclosed set of 󰇛󰇜, 󰇛󰇜
is pairclosed set in 󰇛󰇜.
Theorem 3.6 If 󰇛󰇜󰇛󰇜 is
paircontinuous, and 󰇛󰇜
󰇛󰇜 is paircontinuous, then is
paircontinuous.
Theorem 3.7 If 󰇛󰇜󰇛󰇜 is
paircontinuous and  , then the function
is paircontinuous.
Theorem 3.8 If 󰇛󰇜󰇛󰇜 is
paircontinuous and 󰇛󰇜󰇛󰇜
be pair continuous, then 󰇛󰇜
󰇛 󰇜 represents as 󰇛󰇜
󰇛󰇜󰇛󰇜 is paircontinuous function.
Proof Let be basics of open
subset of 󰇛 󰇜. Then 
󰇛
󰇜
󰇛󰇜
󰇛󰇜. Now, since
WSEAS TRANSACTIONS on MATHEMATICS
DOI: 10.37394/23206.2023.22.105
Ali A. Atoom, Hamza Qoqazeh,
Rahmeh Alrababah, Eman Almuhur,
Nabeela Abu-Alkishik
E-ISSN: 2224-2880
964
Volume 22, 2023
󰇛󰇜󰇛󰇜 be paircontinuous
and 󰇛󰇜󰇛󰇜 be
paircontinuous functions,
󰇛󰇜 is
open and
󰇛󰇜 is open. Thus,

󰇛󰇜 is open. In the same way
for a basics open subset of
󰇛 󰇜. Hence, the function 
is paircontinuous.
Theorem 3.9 Let the function 󰇛󰇜
󰇛󰇜 is defined as 󰇛󰇜
󰇛󰇜󰇛󰇜, where 󰇛󰇜
. Then  is pair continuous if and
only if and are two pair continuous
function.
Proof 󰇜 Assume that  is paircontinuous.
As , where the projection function
󰇛󰇜󰇛󰇜, so by theorem
(3.4) we have is paircontinuous. In the
same way, as we can demonstrate that is
paircontinuous.
󰇜 Assume that the functions and are two
paircontinuous. Let be subset of
󰇛󰇜 such that , where the
set is a open of 󰇛󰇜. Thus 
󰇛󰇜
󰇛󰇜. But the function is
paircontinuous, so the set
󰇛󰇜 is
pairopen. Therefore, the function
󰇛󰇜󰇛 󰇜 is
paircontinuous.
Theorem 3.10 Let 󰇛󰇜󰇛󰇜 be
any function and 󰇛󰇜. If there exist a
pairopen set of 󰇛󰇜 such as , and
the function
is paircontinuous at .
Proof Assume that the subset is open of
󰇛󰇜 containing 󰇛󰇜. Since the function
is paircontinuous at , then there is a
open set of containing such that 󰇛󰇜
󰇡
󰇢󰇛󰇜 . Since the set is pairopen of
󰇛󰇜 and , so since If 󰇛󰇜
󰇛󰇜 is pair continuous and  , then
the function
is paircontinuous , we have
containing . In the same way of the proof,
for the subset is open of 󰇛󰇜 containing
󰇛󰇜. Therefore, the function is
paircontinuous at .
Corollary 3.11 Let the function 󰇛󰇜
󰇛󰇜 and 󰇝 󰇞 be any pairopen
cover of 󰇛󰇜, such as for any .
If the function
is paircontinuous for any
, then is paircontinuous.
It can be observed in the following example that two
pairopen sets do not necessarily have to be
pairopen products.
Example 3.12 Let 󰇛󰇜, 󰇛󰇜
where the set represents the irrational numbers of
and 󰇛󰇜 is subset of . Then is
pairopen set in and is pairopen in , so it
is pairopen set. Moreover, is not
pairopen set.
Question: Let the functions 󰇛󰇜
󰇛󰇜 and 󰇛󰇜󰇛󰇜 be
two paircontinuous. Is the function 
󰇛󰇜󰇛󰇜
󰇛󰇜 paircontinuous.
In fact, the answer will be negative. The example
below demonstrates this.
Example 3.13 Let the set represents the real
numbers and let is the usual topology on .
Assume that 󰇝󰇞 such that 󰇝󰇞,
and the function 󰇛󰇜󰇛󰇜
represents as 󰇛󰇜  is irrational, 󰇛󰇜 is
rational. Now, let the identity function is
󰇛󰇜󰇛󰇜. Thus, it clearly that
the functions and are two
paircontinuous. Now, suppose that the
function  󰇛󰇜󰇛
󰇜 󰇛 󰇜 represents as
󰇛󰇜󰇛󰇜󰇛󰇜. Let the set
󰇝󰇞󰇛󰇜 is open in . So,

󰇛󰇜
󰇛󰇝󰇞󰇜
󰇛󰇜 󰇛󰇜,
but by previous example (3.11), we have 
󰇛󰇜 is
not pairopen. Therefore, the function  is
not paircontinuous.
Definition 3.14 A space 󰇛󰇜 is called
paircompact, if any pairopen cover of
the space has a finite subcover.
Definition 3.15 A space 󰇛󰇜 is called
pairlindelöf, if any pairopen cover of
the space has a countable subcover.
WSEAS TRANSACTIONS on MATHEMATICS
DOI: 10.37394/23206.2023.22.105
Ali A. Atoom, Hamza Qoqazeh,
Rahmeh Alrababah, Eman Almuhur,
Nabeela Abu-Alkishik
E-ISSN: 2224-2880
965
Volume 22, 2023
Definition 3.16 A space 󰇛󰇜 is called
pairclosed compact, if any pair closed
cover of the space has a finite subcover.
Definition 3.17 A space 󰇛󰇜 is called a
countably pairclosed compact, if any
countable pairclosed cover of the space has
a finite subcover.
Theorem 3.18 Let the surjection function
󰇛󰇜󰇛󰇜 is pair continuous.
Then the next statements are hold:
(1) If 󰇛󰇜 is pairlindelöf space, then
󰇛󰇜 is pairlindelöf,
(2) If 󰇛󰇜 is countably paircompact
space, then 󰇛󰇜 is paircountably compact.
Proof (1) Let 󰇝 󰇞 be any
pairopen cover of 󰇛󰇜, since is
surjection function and paircontinuous, then
for any 󰇛󰇜, there exists , for any
is countable subcover such that 󰇛󰇜
󰇋󰇝 󰇞
󰇋󰇝
󰇞

, where the
set 󰇝 󰇞 is open, and 󰇝
󰇞
is open. Now, let the set
󰇡 󰇋
󰇢 is a open containing ,
and the set
󰇡 󰇋
󰇢 is a
open containing , where 󰇛󰇜󰇋
,
󰇛
󰇜󰇋
. Let the cover
󰇝 󰇞󰇝
󰇞 is pairopen of .
Since is pairlindelöf space, then
󰇌
 󰇌
 . Therefore, 󰇛󰇜
󰇌
 󰇌

 .
That is the space is pairlindelöf.
(2) Similar to the prove of part (1).
Corollary 3.19 Let the surjection function
󰇛󰇜󰇛󰇜 is pair continuous.
Then the next statements are hold:
(1) If 󰇛󰇜 is pairlindelöf space, then
󰇛󰇜 is pairlindelöf,
(2) If 󰇛󰇜 is countably pair compact
space, then 󰇛󰇜 is paircountably compact.
Theorem 3.20 Let the surjection function
󰇛󰇜󰇛󰇜 is pair continuous.
Then the next statements are hold:
(1) If 󰇛󰇜 is pairclosed compact space,
then 󰇛󰇜 is paircompact,
(2) If 󰇛󰇜 is pairclosed lindelöf space,
then 󰇛󰇜 is pairlindelöf,
(3) If 󰇛󰇜 is pairclosed compact space,
then 󰇛󰇜 is paircountably compact.
Proof We can prove this theorem in the same way
as the previous theorem (3.18).
Corollary 3.21 Let the surjection function
󰇛󰇜󰇛󰇜 is pair continuous.
Then the next statements are hold:
(1) If 󰇛󰇜is pairclosed compact space,
then 󰇛󰇜 is paircompact,
(2) If 󰇛󰇜is pair closed lindelöf space,
then 󰇛󰇜 is pairlindelöf,
(3) If 󰇛󰇜 is pairclosed compact space,
then 󰇛󰇜 is paircountably compact.
Definition 3.22 A space 󰇛󰇜 is called
pair space, if for any two distinct points
and of 󰇛󰇜, there exists two sets and
is pairopen containing and , respectively,
where and .
Definition 3.23 A space 󰇛󰇜 is called
pair space, if for any two distinct points
and of 󰇛󰇜, there exists two sets and
is pairopen, where and .
Theorem 3.24 Let the injection function
󰇛󰇜󰇛󰇜 is pair continuous
and 󰇛󰇜 is pair space. Then the space
󰇛󰇜 is pair.
Proof Assume that 󰇛󰇜 is pair. For any
two distinct points and of 󰇛󰇜, there
exists open set and open set such that
󰇛󰇜 , 󰇛󰇜 , 󰇛󰇜 , 󰇛󰇜 .
Since is paircontinuous and injection
function, then there are subsets 󰇛󰇜 of
󰇛󰇜 is open and 󰇛󰇜 of
󰇛󰇜 is open, such that
󰇛󰇜, 󰇛󰇜, 󰇛󰇜, 󰇛󰇜.
Thus, the space 󰇛󰇜 is pair.
Corollary 3.25 Let the injection function
󰇛󰇜󰇛󰇜 is pair continuous
and 󰇛󰇜 is pair space. Then the space
󰇛󰇜 is pair .
Theorem 3.26 Let the injection function
󰇛󰇜󰇛󰇜 is pair continuous
and 󰇛󰇜 is pair space. Then the space
󰇛󰇜 is pair.
WSEAS TRANSACTIONS on MATHEMATICS
DOI: 10.37394/23206.2023.22.105
Ali A. Atoom, Hamza Qoqazeh,
Rahmeh Alrababah, Eman Almuhur,
Nabeela Abu-Alkishik
E-ISSN: 2224-2880
966
Volume 22, 2023
Proof Let 󰇛󰇜 is pair space, and the
injection function 󰇛󰇜󰇛󰇜 is
paircontinuous, and in 󰇛󰇜,
then 󰇛󰇜, 󰇛󰇜 are two disjoint subsets of
󰇛󰇜. Since the space 󰇛󰇜 is pair,
there exists two sets open of 󰇛󰇜, and
open , such that 󰇛󰇜 , 󰇛󰇜 ,
. Since is pair continuous and
injection function, then the sets 󰇛 󰇜 be
open in 󰇛󰇜 and containing ,
󰇛 󰇜 be open in 󰇛󰇜 and
containing , such that 󰇟 󰇛 󰇜
󰇛 󰇜󰇠 󰇟󰇛 󰇜󰇛 󰇜󰇠
󰇛 󰇜 󰇛󰇜 . Thus, the space
󰇛󰇜 is pair .
Corollary 3.27 Let the injection function
󰇛󰇜󰇛󰇜 is paircontinuous
and 󰇛󰇜 is pair space. Then the space
󰇛󰇜 is pair .
4 Relations Pairwise Continuous
Function with Forms Continuity
Observe that the paircontinuous functions at
any given point may not always be pairalmost
continuous functions at the same point, as
demonstrated by the next two examples, which also
demonstrate that pairalmost continuous functions
at any given point do not always have to be
paircontinuous at the same point.
Example 4.1 Let the function 󰇛󰇜
󰇛󰇜 defined as 󰇛󰇜 , if is rational
number and 󰇛󰇜 if is irrational number.
Then the function is pairalmost continuous at
any rational number. Nevertheless, the function is
not paircontinuous at each real number.
Example 4.2 Let the real number set be denoted by
, and represents the usual topology on by .
Assume that  󰇝󰇞 with 󰇝󰇝󰇞󰇞.
Now, let 󰇛󰇜 󰇛󰇜 is a function
such that 󰇛󰇜  for irrational and 󰇛󰇜
for rational . Then, for every rational number, is
a paircontinuous function. At any real
number, the function cannot be pairalmost
continuous.
Observe that the pair continuous functions
at any given point may not always be pairweakly
continuous functions at the exact same point, as
demonstrated by the next two examples, which also
demonstrate that pairweakly continuous functions
at any given point do not always have to be
paircontinuous at the exact same point.
Example 4.3 At every irrational number, the
paircontinuous function , as defined in
example [4.1], exists. Nevertheless, the function
cannot be pairweakly continuous.
Example 4.4 Let the real number set be denoted by
, and represents the co-countable topology on
by . Assume that 󰇝󰇞 with
󰇝󰇝󰇞󰇝󰇞󰇝󰇞󰇞. Now, let 󰇛󰇜
󰇛󰇜 is a function such that 󰇛󰇜  for
rational and 󰇛󰇜 for irrational . Then, for
any irrational number, is a pair
continuous function. At any real number, the
function cannot be pair continuous.
Definition 4.5 A function 󰇛󰇜
󰇛󰇜 is called pairsequentially continuous if
for any pairsequence 󰇛󰇜 such that 󰇛󰇜
we have 󰇛󰇜 󰇛󰇜, for .
Note that the function that is defined in example
[4.5] is not pair continuous; more so, it is
pairweakly and pairsequentially continuous.
Conversely, the next example demonstrates that a
paircontinuous function does not necessarily
imply a pairsequentially continuous function.
Example 4.6 Let the function 󰇛󰇜
󰇛󰇜 is identity. Then, the function is
paircontinuous (pair continuous). But the
function cannot be pairsequentially continuous.
󰇛󰇛󰇛󰇜󰇜󰇜
 . Thus 󰇝 󰇞 is a
finite subcover of for . Hence is
compact.
5 Pairwise Barely Continuous
Functions and Pairwise
Lindelöf Space
Theorem 5.1 The following are hold for every
bitopological space 󰇛󰇜:
(1) the space 󰇛󰇜 is pair-lindelöf,
(2) any pair open cover of contains a
countable pairsubcover.
Proof 󰇛󰇜󰇛󰇜 Assume that 󰇝 󰇞 is
pairopen cover of 󰇛󰇜, since
󰇛󰇜 is pairlindelöf, so we have countable
subsets , of the family , then contains
WSEAS TRANSACTIONS on MATHEMATICS
DOI: 10.37394/23206.2023.22.105
Ali A. Atoom, Hamza Qoqazeh,
Rahmeh Alrababah, Eman Almuhur,
Nabeela Abu-Alkishik
E-ISSN: 2224-2880
967
Volume 22, 2023
pairopen cover
,
where is open,
is
open, for any , is countable;
, and is countable. Now, the space is
pairlindelöf gives that contains a countable
pairsubcover󰇥
󰇦󰇥
󰇦. Therefore, the set 
covers by
󰇝󰇞
󰇝󰇞
but the set
󰇝󰇝󰇞
 󰇝󰇞󰇞 is countable, thus
is covered with countably members of . Therefore,
we get the result.
󰇛󰇜󰇛󰇜 is obviously.
Theorem 5.2 Let the function 󰇛󰇜
󰇛󰇜 is paircontinuous. If 󰇛󰇜 is
pairlindelöf, then 󰇛󰇜 is so.
Proof Let
be any
pairopen cover of 󰇛󰇜, where the set
is open and
is
open. Since the function is
paircontinuous, then 󰇛󰇜
󰇛󰇜
is pair open cover of the
space 󰇛󰇜, which the set 󰇛󰇜
is open, and 󰇛󰇜
is
open. Now, since 󰇛󰇜 is pairlindelöf,
by theorem (5.1) we have contains a countable
pairsubcover such that 󰇝󰇛󰇜󰇞
󰇝󰇝󰇛󰇜󰇞
󰇞. Therefore, 󰇝󰇞
󰇝󰇞
is countably pairsubcover
of . Thus, the result.
Corollary 5.3 Let the function 󰇛󰇜
󰇛󰇜 is paircontinuous. If 󰇛󰇜 is
pairlindelöf, then 󰇛󰇜 is so.
Corollary 5.4 Let the function 󰇛󰇜
󰇛󰇜 is paircontinuous. If 󰇛󰇜 is
pairlindelöf, then 󰇛󰇜 is so.
Theorem 5.5 The following are hold for every
bitopological space 󰇛󰇜:
(1) the space 󰇛󰇜 is pair-lindelöf,
(2) any family 󰇝 󰇞 pairclosed sets of
which contains a countable intersection property
that has nonempty intersection.
Definition 5.6 The function 󰇛󰇜
󰇛󰇜 is called pairbarely continuous if for
any nonempty pairclosed 󰇛󰇜, the
restriction
contains there exists one point of
paircontinuity.
Definition 5.7 The function 󰇛󰇜
󰇛󰇜 is called pairbarely continuous if
for any nonempty pairclosed 󰇛󰇜, the
restriction
contains there exists one point of
paircontinuity.
Theorem 5.8 Let the function 󰇛󰇜
󰇛󰇜 is pairbarely continuous. If the
space 󰇛󰇜 is a hereditarily lindelöf, then
󰇛󰇜 is pairlindelöf.
Proof Assume that
is pairopen cover of 󰇛󰇜, which the sets
is open,
is open
and 󰇛󰇜 󰇛󰇜
is
pairopen cover of the space 󰇛󰇜, which
󰇛󰇜 is open, 󰇛󰇜
is open set. Now, let 󰇝 󰇞
󰇝
󰆒 󰇞, the set 󰇝 󰇞 is open,
󰇝
󰆒 󰇞 is open, where is
pairopen subset of 󰇛󰇜 that covered by a
countably numbers of members of . Also, let
󰆒

. Since the space 󰇛󰇜 is
hereditarly lindelöf, we get . Thus, the
elements of is maximal of . Assume that
, then the nonempty subset of 󰇛󰇜 that
is pairclosed. Thus, the function
is
paircontinuous at some . Now, let
such as 󰇛󰇜 , then there a set is
pairopen containing as 󰇛󰇜 .
Additionally, there is a set is pairopen
containing as
is countable. Therefore,
is covered with countably numbers of members of
. Thus, that is contradiction with is a
maximal element of , . So, is covered by
countably subcolletion of . Hence, contains
countable subcover, and so the space 󰇛󰇜 is
pairlindelöf.
Corollary 5.9 Let the function 󰇛󰇜
󰇛󰇜 is pair-barely continuous, then if the
space 󰇛󰇜 is a hereditarily lindelöf, then
󰇛󰇜 is pairlindelöf.
Remark 5.10 Notice that although the function in
example (4.1) is pairbarely continuous, it
cannot be pairbarely continuous.
WSEAS TRANSACTIONS on MATHEMATICS
DOI: 10.37394/23206.2023.22.105
Ali A. Atoom, Hamza Qoqazeh,
Rahmeh Alrababah, Eman Almuhur,
Nabeela Abu-Alkishik
E-ISSN: 2224-2880
968
Volume 22, 2023
6 Conclusions
As we have seen in this research, the functions of
continuous are a generalization of continuous
functions. They have a way to hold onto sequence
limits and are specified on topological spaces. This
implies that the image of a series under the function
will likewise converge to the image of the point if it
contains a sequence of points in the function's
domain that converge to a point. It's a means of
applying the idea of continuity to more complex
circumstances such as weakened these functions, so
based on that we get and explored in this research
their master features, such that the concepts of
pairwise continuous as well as pairwise barely
continuous functions. We have looked at these ideas'
key characteristics and revealed how they relate to
other circumstances. We identified their principal
characteristics as a whole and defined the conditions
that must be met in order to attain comparable
connections between them. We talked about their
main traits and demonstrated how they work
together. The report also highlighted the
characteristics of these functions and offered
numerous instances of them. These functions will
serve as a springboard for research into all of these
functions' possible futures. Future studies might
look into investigating other variations of these roles
such as in fuzzy, soft and group, [30], [31], [32].
Acknowledgements:
We deeply appreciate each person who contributed
to this study. Their teamwork, instructions, and
encouragement have been essential to finishing this
study.
References:
[1] J. C. Kelly, Bitopological spaces, Proc.
Londan Math. Soc, No. 13, 1963, pp. 71-89.
[2] A. For and H. Hdeib, On pairwise Lindelöf
spaces, Rev. Colombiana de Math, No. 17,
1983, pp. 37-58.
[3] Argyros, J. K., & George, S. (2019).
Extending the applicability of the super-
Halley-like method using ω-continuous
derivatives and restricted convergence
domains. In Annales Mathematicae
Silesianae, Vol. 33, pp. 21-40.
[4] Mohammed, I., & Al-Jumaili, A. (2023,
December). Other certain classes of
generalized slightly and almost slightly open
mappings. In AIP Conference Proceedings,
Vol. 2834, No. 1.
[5] W. Al-Luwaici and Ahmad Al-Omari, Some
characteristics of rare ω continuous
functions, Italian Journal of Pure and Applied
Mathematics, No. 48, 2022, pp. 751-759.
[6] H. Z. Hdeib, ω closed mappings, Revista
Colomb. De Mathem. No. 16, 1982, pp. 65-78.
[7] Ali. A. Atoom, study of pairwise ω compact
spaces, Global Journal of Pure and Applied
Mathematics, Vol. 14, No. 11, 2018, pp.
1453-1459.
[8] H. Hdeib, ω Continuous Functions, Dirasat,
XV1, 1989.
[9] A. Killiman and Z. Salleh, Product properties
for pairwise Lindelöf spaces, Bull. Malays.
Math. Sci. Soc. No. 34, 2011, pp. 231-246.
[10] Zorlutunaa, I., Atmacaa, S., & Diria, N. O.
(2023). Minimal continuous multifunctions.
Journal of Linear and Topological Algebra,
12(03), 153-161.
[11] Ali A. Atoom, Hamza Qoqazeh and Nabeela
Abu Alkishik, Lindelöf Perfect Functions, JP
Journal of Geometry and Topology, Vol. 26,
No. 2, 2021, pp.91-101.
[12] Carpintero, C., Rajesh, N., Rosas, E., &
Saranyasri, S. (2020). On Slightly Omega
Continuous Multifunctions. Punjab University
Journal of Mathematics, Vol. 46(1).
[13] Feras Bani-Ahmad, Omar Alsayyed, and Ali
A. Atoom, Some new results of difference
perfect functions in topological spaces, Aims
mathematics, Vol. 7 (11) (2022), 20058–
20065.
[14] Atewi, A. N., Sweedan Naseer, B., Ali, S. J.,
& Harhoosh, M. A. (2022). Forms of $\varpi
$-continuous functions between bitopological
spaces. International Journal of Nonlinear
Analysis and Applications, 13(1), 2219-2225.
[15] Rosas, E., Carpintero, C., Sanabria, J., &
Vielma, J. (2021). Characterizations of upper
and lower (α, β, θ, δ, I)-continuous
multifunctions, Mathematical Studios, Vol.
55, No. 2.
[16] Jubair, W. B., & Ali, H. J. (2022). Contra
ωpre-Continuous functions. Al-Nahrain
Journal of Science, 25(3), 40-42.
[17] Patil, P. G., & Pattanashetti, B. R. (2023).
New Structures of Continuous Functions.
Baghdad Science Journal, 20(1 Special Issue
ICAAM).
WSEAS TRANSACTIONS on MATHEMATICS
DOI: 10.37394/23206.2023.22.105
Ali A. Atoom, Hamza Qoqazeh,
Rahmeh Alrababah, Eman Almuhur,
Nabeela Abu-Alkishik
E-ISSN: 2224-2880
969
Volume 22, 2023
[18] Carpintero, C., Rajesh, N., Rosas, E., &
Saranyasri, S. (2020). On Slightly Omega
Continuous Multifunctions. Punjab University
Journal of Mathematics, Vol.46(1).
[19] Sahloli, A. M., & Al Shumrani, M. A. (2020).
On ω-leaders and ω-continuous Maps.
Proceedings of the Bulgarian Academy of
Sciences, 73(9), No.9, pp.1210-1216.
[20] Ekici, E., Jafari, S., & Moshokoa, S. P.
(2010). On a weaker form of ω-
continuity. Annals of the University of
Craiova-Mathematics and Computer
Science Series, 37(2), 38-46.
[21] Saif, A., Al-Audhahi, A. M., & Dawood, S.
(2022). On Continuity of Grill Topological
Spaces VIA Regular Generalized
G\(\omega\)-Closed Sets. Asian Research
Journal of Mathematics, Vol. 18, Issue 11,
77-91.
[22] Therasa, J., Senthilkumaran, V., &
Palaniappan, Y. (2019). On g* ω Closed Sets
in Topological Spaces. Journal of Computer
and Mathematical Sciences, 10(5), 1016-
1020.
[23] Roy, B., & Sen, R. (2022). On ω*-open sets
and decomposition of continuity. Topological
Algebra and its Applications, 10(1), 154-160.
[24] S. Bose and D. Sinha, Pairwise almost
continuous map and weakly continuous map
in bitopological spaces, Bull. Cal. Math. Soc.
No. 74, 1982, pp. 195-206.
[25] T. Birsan, Compactness in ditopogical spaces
(Compacite dans les espaces ditopogiques),
St. Univ. Iasi,s.i.a., Mathematica, No. 15,
1969, pp. 317-328.
[26] M. C. Datta, Projection Bitopological Spaces,
J. Austral. Math. Soc., No. 13, 1972, pp. 327-
334.
[27] P. Fletcher, Hughes B. Hoyle, III, C. W. Patty,
The comparison of topologies, Duke. Math. J.
No. 36, 1969, pp. 325-331.
[28] E. Ryszard, General topology, Second edition,
Berlin, Heldermann, 1989.
[29] Al Ghour, S. (2023). Soft functions via soft
semi ω-open sets. J. Math. Comput. Sci, 30,
133-146.
[30] Carpintero, C., Rajalakshmi, R., Rajesh, N., &
Rosas, E. (2022). Weakly ω-continuous
functions in bitopological spaces. Italian
Journal of Pure and Applied Mathematics, 47,
401-412
[31] Ghour, S. A., & Al-Saadi, H. (2023). Soft ω-
θ-Continuous and Soft Weakly θ ω-
Continuous Mappings. Mathematics, 11(19),
4092.
[32] Ahlam Fallatah, Mourad Oqla massa'deh,
Abd ULazeez Alkouri, homomorphism Of
Tripolar Fuzzy Soft Γ−Semiring, Wseas
Transactions on mathematics,Vol. 19, 2020,
No.10, pp. 37394/23206
Contribution of Individual Authors to the
Creation of a Scientific Article (Ghostwriting
Policy)
- Ali Atoom: presented the main idea of the
research, provided the basic definition of the
research, and enriched it with several theories and
illustrative examples.
- Hamza Qoqazeh: wrote the introduction of the
research and added some theories and scientific
facts to the research.
- Rahmeh Alrababah: wrote the introduction of the
research and added some theories and scientific
facts to the research.
- Eman Almuhur: conducted scientific and
linguistic scrutiny of the research, as well as
reviewed and verified the academic references.
- Nabeela Abu-Alkishik: conducted scientific and
linguistic scrutiny of the research, as well as
reviewed and verified the academic references.
Sources of Funding for Research Presented in a
Scientific Article or Scientific Article Itself
This research was funded by Ajloun National
University.
Conflict of Interest
The authors acknowledge the work's authorship and
declare that no personal gain is intended from its
publication. The primary aim of this study is to
make a scientific contribution to the area of general
topology. Furthermore, every researcher certifies
that this work was not published, submitted to, or
accepted for publication in any journal and that it
was entirely new research.
Creative Commons Attribution License 4.0
(Attribution 4.0 International, CC BY 4.0)
This article is published under the terms of the
Creative Commons Attribution License 4.0
https://creativecommons.org/licenses/by/4.0/deed.en
_US
WSEAS TRANSACTIONS on MATHEMATICS
DOI: 10.37394/23206.2023.22.105
Ali A. Atoom, Hamza Qoqazeh,
Rahmeh Alrababah, Eman Almuhur,
Nabeela Abu-Alkishik
E-ISSN: 2224-2880
970
Volume 22, 2023