What does tautology mean?
A tautology is a statement that conveys no new information because it repeats an idea already expressed. Phrases such as “he arrived at the appointed time” may do useful work in ordinary communication, but a tautology adds redundancy rather than meaning, and the term is often used to criticize verbose or circular writing. Tautology also has a precise role in logic, where it denotes a proposition that is true in every possible case, regardless of how its components are interpreted. This technical sense differs from the everyday criticism of needless repetition. The word is useful because it identifies a common fault in reasoning and style: expressions that appear substantial but add nothing beyond what has already been stated. Although generally neutral in formal logic, it often sounds critical or technical in literary and rhetorical discussion.
nounA tautology is a statement or expression that repeats the same idea without adding new information. In logic, it is a proposition or formula that is true in every possible case.
- A statement or expression that repeats the same idea in different words without adding information.
- In logic, a proposition or formula that is true in every possible case.
"His claim that the deadline would be met on time was a tautology."
"The opening paragraph is little more than a tautology."
"The equation remains true regardless of the value assigned to the variable, making it a logical tautology."
The standard plural is formed by adding -ies to the singular.
"The editor removed several tautologies from the speech."
Tautology comes from Greek roots meaning “the same” and “an account,” so it literally describes words that keep saying the same thing.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does tautology come from?
Tautology comes from Greek tautologos, meaning “repeating the same thing,” formed from tautos, “the same,” and logos, “an account” or “statement.” The Greek expression referred to repetition of the same idea, and English later developed both the general sense of verbal redundancy and the specialized logical sense of a proposition that is always true. The same roots produced related English forms such as tautological, tautologically, and tautologist.
Related word forms
How tautology is actually used
The word is primarily formal and often carries a mildly critical connotation, especially when discussing rhetoric, writing, or argument. In general usage it denotes unnecessary repetition; in logic it more precisely names a proposition that must be true because of its structure.
Easily confused with tautology
A tautology is necessarily true but uninformative, whereas a paradox appears contradictory or surprising and may require resolution or may remain false.