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Keyword vs. Identifier: What's the Difference?

Edited by Aimie Carlson || By Harlon Moss || Updated on October 17, 2023
A keyword is a reserved word in programming; an identifier names variables, functions, etc.

Key Differences

Keywords in programming languages are reserved words with predefined meanings. Identifiers, on the other hand, are user-defined names given to various programming elements, such as variables and functions.
While keywords hold a consistent meaning and cannot be altered, identifiers allow programmers the flexibility to choose names, ensuring code readability and organization.
One cannot use a keyword as an identifier because the programming language already assigns specific functionality to that keyword. Conversely, an identifier can't function as a keyword since it lacks built-in meaning.
In essence, keywords act as the building blocks of a programming language, guiding its syntax and structure. Identifiers, however, provide individuality to a programmer's code, representing specific data or actions.
While the list of keywords is fixed for a specific programming language, the potential identifiers a programmer can use is virtually limitless, only bound by naming conventions and rules.

Comparison Chart


Reserved word with predefined meaning
User-defined name for programming elements


Fixed and unchangeable within a language
Can be named flexibly based on user preference

Usage Restrictions

Cannot be used as an identifier
Cannot function as a keyword

List Limitation

Limited set in each programming language
Virtually limitless, adhering to naming rules

Main Purpose

Guide the syntax and structure of a language
Represent specific data or actions in code

Keyword and Identifier Definitions


A word serving as a key to a code or cipher.
The keyword helped them decode the message.


A distinguishing feature or characteristic.
Her tattoo is an identifier that sets her apart.


A significant word used to index content.
The article had the keyword sustainability.


A user-defined name for elements like variables in programming.
In the code, totalAmount is an identifier for a variable.


A reserved word in programming languages.
The word return is a keyword in many programming languages.


A name or term establishing identity.
The product's barcode is its primary identifier.


A word used for search engine queries.
She entered the keyword chocolate cake recipe into the search engine.


A label used to reference data.
Each database entry has a unique identifier.


A term representing the essence of a topic.
Innovation is a keyword for tech startups.


A unique name or symbol denoting an entity.
The chemical formula serves as an identifier for the compound.


A word that serves as a key to a code or cipher.


To establish or recognize the identity of; ascertain as a certain person or thing
Can you identify what kind of plane that is? I identified the man at the next table as a famous actor.


A significant or descriptive word.


(Biology) To determine the taxonomic classification of (an organism).


What's the difference between a keyword and a keyword phrase?

A keyword is a single word, while a keyword phrase consists of multiple words, often used in search queries.

Are identifiers case-sensitive?

Typically, yes. In most programming languages, identifiers are case-sensitive.

Can I name a variable after a keyword?

No, keywords are reserved and cannot be used as identifiers in programming.

Can two variables have the same identifier name?

No, within the same scope, identifiers must be unique.

Why are keywords important in search engines?

Keywords help index content, making it discoverable based on user queries.

What's the main function of a keyword in programming?

Keywords dictate the structure and syntax of a programming language.

Are all keywords in programming languages universal?

No, keywords can vary between different programming languages.

How do I choose a good identifier name in coding?

Choose descriptive, concise names that reflect the identifier's purpose, adhering to naming conventions.

Why can't we use keywords as variable names?

Keywords have predefined meanings, using them as variable names would create ambiguity.

Are all keywords in a programming language always in use?

Not necessarily. Some might be reserved for future use or exist for legacy reasons.

Do keyword and identifier have meanings outside of programming?

Yes. A keyword can mean a significant term, and identifier can mean a distinguishing feature.

What is the main role of an identifier in programming?

Identifiers name and distinguish various programming elements like variables, functions, etc.

Can keywords be used in search engine optimization (SEO)?

Yes, keywords are crucial in SEO for indexing and ranking content.

Can I use a keyword in a string or comment?

Yes, within strings or comments, keywords are treated as plain text, not reserved words.

Are there rules for creating identifiers?

Yes, most languages have rules, like not starting with numbers or avoiding special characters.

How do identifiers relate to data types?

Identifiers name elements like variables, which have associated data types determining the kind of data stored.

Can an identifier be a number?

In most languages, identifiers can contain numbers but shouldn't start with one.

Do keywords change over time?

Rarely. However, new versions of a language might introduce new keywords or deprecate old ones.

Are there conventions for naming identifiers?

Yes, like camelCase or snake_case, which improve code readability.

Can I create custom keywords in a programming language?

No, keywords are fixed. However, you can create functions or macros and name them using identifiers.
About Author
Written by
Harlon Moss
Harlon is a seasoned quality moderator and accomplished content writer for Difference Wiki. An alumnus of the prestigious University of California, he earned his degree in Computer Science. Leveraging his academic background, Harlon brings a meticulous and informed perspective to his work, ensuring content accuracy and excellence.
Edited by
Aimie Carlson
Aimie Carlson, holding a master's degree in English literature, is a fervent English language enthusiast. She lends her writing talents to Difference Wiki, a prominent website that specializes in comparisons, offering readers insightful analyses that both captivate and inform.

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