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tautology

taw-TOL-uh-jee /tɔːˈtɒl.ə.dʒi/

nounC2GRESAT

academicformal

A statement that is redundantly true by necessity of its own logical form, repeating the same idea twice in different words.

In daily language, it is a stylistic fault (e.g., 'free gift', 'unmarried bachelor'). In formal logic, it is a statement that is true under every possible interpretation (e.g., 'It will rain or it will not rain').

The story behind the word. From Greek 'tauto' (the same) and 'logos' (word/speech). Literally translates to 'saying the exact same thing again'. It entered English in the 16th century to criticize lazy speakers who repeated definitions as proofs.

Word relationships

redundancy: Redundancy is the unnecessary repetition of words or components; tautology is a specific statement whose logic repeats itself.

contradiction: A statement that is necessarily false by virtue of its logical form (e.g., 'It is raining and it is not raining').

Commonly confused with

paradox: A tautology is self-evidently true and redundant; a paradox seems self-contradictory yet exposes a deeper truth.

Word family

tautological (adjective): Containing unnecessary repetition or logically redundant.
tautologically (adverb): In a tautological manner.

Collocations

empty tautology
mere tautology
linguistic tautology
logical tautology

Example sentences

"To say 'he arrived one after another in single file' is a classic linguistic tautology that adds no new information." Linguistics
"The proposition 'Either the team wins or the team does not win' is a pure logical tautology." Logic Lecture

Memory hook

TAUTO-logy is TALKING TOTAL SAMENESS: repeating ideas like 'free gift'. Saying the same thing twice in different words.

When not to use

Do not use to describe a contradiction or a lie. A tautology is always true, but completely uninformative.

Fun facts

The famous slogan 'It is what it is' is one of the most widely spoken modern tautologies in the English language!