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Identifier vs. Keyword — What's the Difference?

By Maham Liaqat & Fiza Rafique — Published on March 7, 2024
Identifier is a name given to entities like variables and functions in programming, allowing for unique identification, whereas a keyword is a reserved word with a predefined meaning in a programming language's syntax.
Identifier vs. Keyword — What's the Difference?

Difference Between Identifier and Keyword


Key Differences

Identifiers are the custom names programmers give to different entities such as variables, functions, and classes to identify them uniquely within a program. Keywords, on the other hand, are predefined words by the programming language itself, serving specific purposes and cannot be used as identifiers.
Identifiers can be created following certain rules such as beginning with a letter or an underscore, while keywords are fixed and form the core syntax of the programming language. For example, if, else, while are keywords that cannot be altered.
The choice of identifiers is at the discretion of the programmer and plays a crucial role in making the code readable and maintainable. Keywords are integral to the language and are used to perform specific operations, like controlling the flow of the program.
Identifiers must be unique in their scope and can be reused across different scopes. Keywords are universally recognized by the compiler or interpreter of the language and their meaning or function cannot change.
A good understanding of both identifiers and keywords is essential for effective programming. Identifiers allow for flexibility and creativity in naming, while keywords ensure that the programming language has a standardized syntax.

Comparison Chart


Custom names given to program entities.
Predefined words with special syntax role.


To uniquely identify variables, functions.
To define the structure and syntax of code.


Can be chosen freely following naming rules.
Fixed and cannot be used as identifiers.

Scope of Use

Unique within their scope.
Universally recognized and consistent.

Role in Programming

Enhance code readability and maintenance.
Control the flow and structure of code.

Compare with Definitions


Variable Name
TotalSum represents the sum of various elements.


If (condition) { ... } executes a block of code if the condition is true.


Class Name
Person could represent a class in a program managing human attributes.


Else { ... } executes a block of code if the if condition is false.


Function Name
CalculateArea() computes the area of a given shape.


For (initialization; condition; increment) { ... } creates a loop.


Module Name
MathOperations could be a module containing various mathematical functions.


Class Dog { ... } defines a new class.


Constant Name
MAX_LIMIT defines a constant value representing maximum limit.


Return x; exits a function and possibly returns a value.


To ascertain as having a certain characteristic or feature
Job candidates who are identified as overqualified.
Children who have been identified with hearing loss.


A significant or descriptive word.


A guidebook that helps determine the specific class of an object (such as a mushroom, herb, fish, bird, drug, or mineral), or its individual identity (such as that of a star).


A word used as a reference point for finding other words or information.


(HTML) A code that distinguishes a particular element from all other elements in a document.


(cryptography) Any word#Noun used as the key to a code.


A symbol that establishes the identity of the one bearing it


(programming) A reserved word used to identify a specific command, function, etc.

Common Curiosities

What is an identifier?

An identifier is a name given to entities like variables and functions in programming for identification.

How do identifiers and keywords differ in usage?

Identifiers are defined by programmers and are used for naming variables, functions, etc., while keywords are predefined and control the structure and flow of programs.

Can a keyword be used as an identifier?

No, keywords cannot be used as identifiers because they have specific meanings and roles in programming languages.

Can keywords be added to a programming language?

Keywords are added to programming languages by their designers and cannot be modified by programmers.

Are identifiers case-sensitive?

Yes, in most programming languages, identifiers are case-sensitive.

What is a keyword?

A keyword is a reserved word in a programming language that has a predefined meaning in its syntax.

How are identifiers chosen?

Identifiers are chosen by programmers and must follow specific naming rules such as starting with a letter or an underscore.

Do all programming languages have the same keywords?

No, different programming languages have different sets of keywords.

Can the same identifier be used for different entities in a program?

No, an identifier must be unique within its scope but can be reused in different scopes.

Why are keywords important in programming?

Keywords are crucial for defining the syntax and structure of programs, allowing for operations like looping, condition checking, and class definition.

Is it possible to create custom keywords in a programming language?

No, programmers cannot create custom keywords; they are defined by the language's design.

How does the scope of an identifier affect its usage?

An identifier's scope determines where it is recognized in the program, affecting its visibility and reusability.

What happens if a keyword is incorrectly used as an identifier?

The program will generate a syntax error, as keywords have predefined functions in the language's syntax.

Are there any restrictions on naming identifiers?

Yes, identifiers must follow specific rules related to characters used and cannot conflict with keywords.

Can the use of identifiers affect program performance?

While identifiers themselves don't affect performance, their proper use can make the code more readable and maintainable.

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Author Spotlight

Written by
Maham Liaqat
Co-written by
Fiza Rafique
Fiza Rafique is a skilled content writer at, where she meticulously refines and enhances written pieces. Drawing from her vast editorial expertise, Fiza ensures clarity, accuracy, and precision in every article. Passionate about language, she continually seeks to elevate the quality of content for readers worldwide.

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