exˌtensioˈnality
C2Formal, Technical, Academic
Definition
Meaning
In a manner related to or defined by the external properties, behavior, or referents of something, rather than its internal structure or description.
In logic and philosophy of language: the principle or method of evaluating meaning or truth based on extensions (i.e., the set of objects a term refers to, or the truth-values of statements), as opposed to intensions (concepts, senses, or internal definitions).
Linguistics
Semantic Notes
Primarily a technical term in logic, philosophy of language, and computer science (especially semantics of programming languages). It is an adverb derived from 'extensional'. Its use is almost entirely confined to discussions about meaning, reference, and equivalence.
Dialectal Variation
British vs American Usage
Differences
No significant difference in meaning or usage. Spelling follows regional norms for '-ly' adverb formation.
Connotations
Highly technical and precise in both varieties.
Frequency
Extremely rare in general usage, but used with equal technical specificity in British and American academic writing.
Vocabulary
Collocations
Grammar
Valency Patterns
[Subject] + [verb of definition/equivalence] + extensionally[Concept/Theory] + is + based + extensionally + on [criterion]Vocabulary
Synonyms
Strong
Neutral
Weak
Vocabulary
Antonyms
Phrases
Idioms & Phrases
- “(no common idioms)”
Usage
Context Usage
Business
Virtually never used.
Academic
Core term in analytic philosophy, logic, and formal semantics. E.g., 'Two sets are equal if they are extensionally equivalent.'
Everyday
Extremely unlikely to be encountered or used.
Technical
Used in theoretical computer science, especially in formal methods and programming language theory discussing semantic equivalence.
Examples
By Part of Speech
verb
British English
- The theory defines predicate truth extensionally.
- We can characterise the set extensionally.
American English
- The model interprets the symbols extensionally.
- They specified the function extensionally.
adverb
British English
- The two concepts are equivalent only if viewed extensionally.
- The law applies extensionally to all cases.
American English
- We must think extensionally about this problem.
- The system's behavior is defined extensionally.
adjective
British English
- This is an extensional treatment of meaning.
- An extensional definition lists members.
American English
- He provided an extensional account of the concept.
- Extensional equivalence is crucial.
Examples
By CEFR Level
- (Not applicable for this level.)
- (Not applicable for this level.)
- In simple terms, to define a set extensionally means to list all its elements.
- Philosophers debate whether natural kind terms like 'water' can be defined purely extensionally by their physical composition.
- The two computer programs are considered equivalent extensionally because they produce identical outputs for all inputs.
Learning
Memory Aids
Mnemonic
Think of an EXTENSIONAL garden hose: what matters is which flowers it reaches (its extension), not what colour the hose is (its intension). To think EXTENSIONALLY is to care about what things it connects to.
Conceptual Metaphor
MEANING AS A LIST: Understanding a word extensionally is like defining it by writing a list of everything it applies to.
Watch out
Common Pitfalls
Translation Traps (for Russian speakers)
- Do not confuse with 'расширительно' (in an expanded sense).
- The Russian philosophical term 'экстенсионально' is a direct cognate but is itself a high-register loanword.
- Avoid translating it as 'внешне' (externally in a physical sense); it's a logical, not spatial, term.
Common Mistakes
- Confusing 'extensionally' (adverb) with 'extensionality' (noun).
- Using it in non-technical contexts where 'generally' or 'broadly' is intended.
- Misspelling as 'extentionally'.
Practice
Quiz
In which field is the term 'extensionally' MOST commonly used?
FAQ
Frequently Asked Questions
It means 'by what things it refers to' or 'by its external effects/outputs', not by its internal meaning or description.
No, it is a highly specialized term used almost exclusively in academic discussions about logic, language, and meaning.
'Extensively' means 'to a great degree or over a large area'. 'Extensionally' is a technical term about reference and equivalence. They are false friends.
The terms 'creature with a kidney' and 'creature with a heart' are extensionally equivalent if, in the real world, exactly the same animals have kidneys as have hearts. Their meanings (intensions) are different, but their extensions are the same.