Token vs. Lexeme — What's the Difference?
By Urooj Arif & Fiza Rafique — Updated on March 31, 2024
A token represents an instance of a sequence of characters in source code that are grouped together as a useful semantic unit for parsing, whereas a lexeme is the lowest level syntactic unit of a language that cannot be further divided.
Difference Between Token and Lexeme
Table of Contents
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Key Differences
Tokens are the building blocks of a program's syntax, identified during the lexical analysis phase of compilation or interpretation. Lexemes, on the other hand, are the abstract representations of the sequence of characters that form these tokens, considered in their syntactic role without reference to their meaning in a program.
Tokens are often the result of the lexical analysis process, where the source code is scanned and divided into meaningful symbols defined by the language's syntax. Lexemes, while closely related, are more about the theory and definition of these symbols. They provide the basis for the language's lexicon, much like words do in natural language.
The relationship between tokens and lexemes is akin to that between a class and its instances in object-oriented programming. The token is a general category of syntactic elements (like identifiers, keywords, operators), while the lexeme is a specific example of these categories appearing in the source code. For instance, every occurrence of if in the code is a lexeme belonging to the token type KEYWORD.
Understanding the distinction between tokens and lexemes is crucial for compilers and interpreters, as it helps in syntactic analysis and the transformation of source code into executable programs. While tokens are used in the parsing phase to understand and structure the program, lexemes are foundational in defining the language's grammar and syntax rules.
Comparison Chart
Definition
An instance of a sequence of characters grouped as a meaningful semantic unit for parsing
The lowest level syntactic units that form the vocabulary of a language
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Role in Compilation
Categorized based on the role in syntax (e.g., keyword, identifier)
Represent sequences of characters as abstract syntactic entities
Analysis Phase
Identified and categorized during lexical analysis
Form the basis for defining token types in the language's grammar
Relation
The categorized instance of a lexeme in the source code
The abstract concept or the sequence of characters that constitutes a token type
Compare with Definitions
Token
A categorized symbol in the source code during lexical analysis.
In return 0;, return and 0 are tokens representing a keyword and a literal, respectively.
Lexeme
Fundamental vocabulary of a programming language.
Lexemes form the basic elements from which tokens are categorized for parsing.
Token
Used in syntax analysis and parsing.
Parsing algorithms use tokens to construct the syntax tree of a program.
Lexeme
The lowest level unit in the syntax of programming languages.
In the declaration float rate = 3.14;, rate and 3.14 are lexemes.
Token
The syntactic category for a sequence of characters.
Every variable name is identified as the IDENTIFIER token in a program.
Lexeme
Indivisible syntactic entities of a language.
Each identifier used in a program is a lexeme representing a variable, function, or type name.
Token
Represents meaningful elements for the compiler.
Operators like + and * are specific tokens that indicate arithmetic operations.
Lexeme
A sequence of characters with a collectively assigned meaning.
Keywords like if, else, and while are lexemes in most programming languages.
Token
A component of programming language grammar.
Tokens are essential for parsing the program's source code.
Lexeme
The abstract representation of program symbols.
Numeric constants in code, regardless of value, are considered lexemes.
Token
Something serving as an indication, proof, or expression of something else; a sign
"His lifelong refusal to allow bigots to truly bother him was often considered, unfairly, a token of his weakness" (Jeremy Schaap).
Lexeme
A lexeme ( (listen)) is a unit of lexical meaning that underlies a set of words that are related through inflection. It is a basic abstract unit of meaning, a unit of morphological analysis in linguistics that roughly corresponds to a set of forms taken by a single root word.
Token
Something that signifies or evidences authority, validity, or identity
The scepter is a token of regal status.
Lexeme
The fundamental unit of the lexicon of a language. Find, finds, found, and finding are forms of the English lexeme find.
Token
A specific instance of a phenomenon or a class of things, as of a linguistic feature in a sample of a person's speech, that can be isolated for study or analysis.
Lexeme
(linguistics) A lexical item corresponding to the set of all words (or of all multi-word expressions) that are semantically related through inflection of a particular shared basic form.
Token
A person who is considered as representative of a social group, such as a lone individual or one of a small number of employees hired primarily to prevent an employer from being accused of discrimination.
Lexeme
(strictly) The abstract minimum unit of language or meaning that underlies such a set.
Token
A keepsake or souvenir.
Lexeme
(loosely) The set itself; a lexemic family.
Token
A piece of stamped metal used as a substitute for currency
Subway tokens.
Lexeme
(loosely) The word-form chosen to represent such a set or family.
Token
A small electronic device issued to a user to serve as proof of identity, as for the purpose of accessing a network.
Lexeme
(computing) An individual instance of a continuous character sequence without spaces, used in lexical analysis (see token).
Token
A piece of software that serves as proof of the user's identity.
Lexeme
A minimal unit (as a word or stem) in the lexicon of a language; `go' and `went' and `gone' and `going' are all members of the English lexeme `go'
Token
To betoken or symbolize; portend.
Token
Done as an indication or pledge
A token payment.
Token
Perfunctory; minimal
A token gesture of reconciliation.
Token resistance.
Token
Being a product of tokenism; merely symbolic
Refused to be the token woman on the committee.
Token
Something serving as an expression of something else.
According to the Bible, the rainbow is a token of God's covenant with Noah.
Token
A keepsake.
Please accept this bustier as a token of our time together.
Token
A piece of stamped metal or plastic, etc., used as a substitute for money; a voucher that can be exchanged for goods or services.
Subway tokens are being replaced by magnetic cards.
A book token is the easiest option for a Christmas gift.
Token
A small physical object, often designed to give the appearance of a common thing, used to represent a person or character in a board game or other situation.
Everyone pick a token (hat, wheelbarrow, thimble, etc.) and place it on the Start square.
Token
A minor attempt for appearance's sake, or to minimally comply with a requirement.
His apology was no more than a token.
Token
A member of a group of people that is included within a larger group to comply with a legal or social requirement.
Token
Evidence, proof; a confirming detail; physical trace, mark, footprint.
Token
Support for a belief; grounds for an opinion.
Token
An extraordinary event serving as evidence of supernatural power.
Token
An object or disclosure to attest or authenticate the bearer or an instruction.
Token
A seal guaranteeing the quality of an item.
Token
Something given or shown as a symbol or guarantee of authority or right; a sign of authenticity, of power, good faith.
Token
A tally.
Token
(philosophy) A particular thing to which a concept applies.
Token
(computing) An atomic piece of data, such as a word, for which a meaning may be inferred during parsing.
Token
(computing) A conceptual object that can be possessed by a computer, process, etc. in order to regulate a turn-taking system such as a token ring network.
Token
(computing) A meaningless placeholder used as a substitute for sensitive data.
Token
(grammar) A lexeme; a basic, grammatically indivisible unit of a language such as a keyword, operator or identifier.
Token
(corpus linguistics) A single example of a certain word in a text or corpus.
Token
(medical) A characteristic sign of a disease or of a bodily disorder, a symptom; a sign of a bodily condition, recovery, or health.
Token
A livid spot upon the body, indicating, or supposed to indicate, the approach of death.
Token
(printing) Ten and a half quires, or, commonly, 250 sheets, of paper printed on both sides; also, in some cases, the same number of sheets printed on one side, or half the number printed on both sides.
Token
(mining) A bit of leather having a peculiar mark designating a particular miner. Each hewer sent one of these with each corf or tub he had hewn.
Token
(mining) A thin bed of coal indicating the existence of a thicker seam at no great distance.
Token
(rail transport) A physical object used for exchange between drivers and signalmen on single track lines.
Token
(weaving) In a loom, a colored signal to show the weaver which shuttle to use.
Token
(Church of Scotland) A piece of metal given beforehand to each person in the congregation who is permitted to partake of the Lord's Supper.
Token
Done as an indication or a pledge.
Token
Perfunctory or merely symbolic; done or existing for appearance's sake, or to minimally comply with a requirement.
A token gesture
He made a token tap on the brake pedal at the stop sign.
Token
(of people) Included in minimal numbers in order to create an impression or illusion of diversity, especially ethnic or gender diversity.
He was hired as the company's token black person.
The television show was primarily directed toward a black audience, but it did have a few token white people as performers.
Token
To betoken, indicate, portend, designate, denote
Token
To betroth
Token
(philosophy) To symbolize, instantiate
Token
Something intended or supposed to represent or indicate another thing or an event; a sign; a symbol; as, the rainbow is a token of God's covenant established with Noah.
Token
A memorial of friendship; something by which the friendship of another person is to be kept in mind; a memento; a souvenir.
This is some token from a never friend.
Token
Something given or shown as a symbol or guarantee of authority or right; a sign of authenticity, of power, good faith, etc.
Say, by this token, I desire his company.
Token
A piece of metal intended for currency, and issued by a private party, usually bearing the name of the issuer, and redeemable in lawful money. Also, a coin issued by government, esp. when its use as lawful money is limited and its intrinsic value is much below its nominal value.
Token
A livid spot upon the body, indicating, or supposed to indicate, the approach of death.
Like the fearful tokens of the plague,Are mere forerunners of their ends.
Token
Ten and a half quires, or, commonly, 250 sheets, of paper printed on both sides; also, in some cases, the same number of sheets printed on one side, or half the number printed on both sides.
Token
A piece of metal given beforehand to each person in the congregation who is permitted to partake of the Lord's Supper.
Token
A bit of leather having a peculiar mark designating a particular miner. Each hewer sends one of these with each corf or tub he has hewn.
Token
In a Jacquard loom, a colored signal to show the weaver which shuttle to use.
Token
To betoken.
Token
An individual instance of a type of symbol;
The word`error' contains three tokens of `r'
Token
A metal or plastic disk that can be used (as a substitute for coins) in slot machines
Token
Something of sentimental value
Token
Insignificantly small; a matter of form only (`tokenish' is informal);
The fee was nominal
A token gesture of resistance
A tokenish gesture
Common Curiosities
Can a lexeme belong to different token types?
No, a lexeme is associated with a specific token type based on its role in the language's syntax.
How does a compiler use tokens and lexemes?
A compiler uses lexemes to define the language's vocabulary and tokens for parsing and syntactic analysis.
Are tokens and lexemes the same in every programming language?
The concept is universal, but the specific tokens and lexemes differ across languages based on syntax and grammar.
Why are tokens and lexemes important in programming?
They are crucial for the lexical analysis phase, helping compilers and interpreters to parse and understand the source code.
How are tokens and lexemes related to syntax errors?
Syntax errors often occur when the compiler encounters tokens that don't conform to the language's grammar rules.
What is the first step in compiling a program?
Lexical analysis, where the source code is broken down into tokens and lexemes are identified.
Can a single character be a lexeme?
Yes, if it has meaning by itself in the language's syntax, such as an operator or delimiter.
Is understanding tokens and lexemes essential for programmers?
While not required for basic programming tasks, a deeper understanding can be crucial for debugging, language design, and compiler development.
Do all programming languages use the concept of tokens and lexemes?
Yes, these concepts are fundamental to the process of compiling or interpreting any programming language.
Are whitespace characters considered lexemes?
Whitespace may be significant for token separation but typically does not constitute lexemes unless specifically defined in the language's syntax.
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Written by
Urooj ArifUrooj is a skilled content writer at Ask Difference, known for her exceptional ability to simplify complex topics into engaging and informative content. With a passion for research and a flair for clear, concise writing, she consistently delivers articles that resonate with our diverse audience.
Co-written by
Fiza RafiqueFiza Rafique is a skilled content writer at AskDifference.com, 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.
