[ taw-tol-uh-jee ]
/ tɔˈtɒl ə dʒi /
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See synonyms for: tautology / tautological / tautologous on Thesaurus.com

noun, plural tau·tol·o·gies.
needless repetition of an idea, especially in words other than those of the immediate context, without imparting additional force or clearness, as in “widow woman.”
an instance of such repetition.
  1. a compound propositional form all of whose instances are true, as “A or not A.”
  2. an instance of such a form, as “This candidate will win or will not win.”
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Origin of tautology

First recorded in 1570–80; from Late Latin tautologia, from Greek tautología “repetition of something already said” (a term in rhetoric); see origin at tauto-, -logy


tau·to·log·i·cal [tawt-l-oj-i-kuhl], /ˌtɔt lˈɒdʒ ɪ kəl/, tau·to·log·ic, tau·tol·o·gous [taw-tol-uh-guhs], /tɔˈtɒl ə gəs/, adjectivetau·tol·o·gist, noun


redundancy, tautology
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023


What does tautology mean?

A tautology is the unnecessary repetition of an idea, statement, or word whose meaning has already been expressed, as in 8 a.m. in the morning. (The label a.m. indicates the morning, so in the morning creates a tautology).

Tautologies say the same thing twice without adding new information or emphasis.

In logic, tautology has a more specific meaning: a statement that is always true, as in Statement 1 is true or not true or Either we will arrive on time or we will not arrive on time.  

Example: My professor pointed out that the phrase “evening sunset” is a tautology because sunsets always happen in the evening.

Where does tautology come from?

The first records of the word tautology come from the 1500s. It comes from the Greek tautología. The combining form tauto- means “same,” and the ending -logy can be used in reference to writing or discourse.

Tautologies are often avoided in writing because they consist of an unnecessary repetition of the same information without adding any emphasis. Of course, this is sometimes a matter of preference. The phrases dilapidated ruins and dry desert can be considered tautologies because the adjective in each expresses something already expressed by the noun. But it could be argued that they add emphasis. Some tautologies are more obvious, as in She’s a beginner who just started or We are currently closed at this time. 

In logic, tautology refers to a statement that’s true in every interpretation, as in Either we will win or we will not win. 

The word redundancy is similar, but it’s usually used more generally, often for the simple repetition of a specific word, as in The Department of Redundancy Department or $20 dollars (in which dollars is unnecessary due to the use of the symbol $). By contrast, an oxymoron is a phrase or expression that uses terms that contradict each other, as in the phrase growing smaller.

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What are some other forms related to tautology?

  • tautological (adjective)
  • tautologic (adjective)
  • tautologous (adjective)
  • tautologism (noun)
  • tautologize (verb)
  • tautologically (adverb)
  • tautologously (adverb)
  • nontautological (adjective)

What are some words that share a root or word element with tautology

What are some words that often get used in discussing tautology?


How is tautology used in real life?

The word tautology is often discussed in the context of writing as something to avoid. When spotted in real life, tautologies are often humorous.



Try using tautology!

Which of the following phrases is an example of a tautology

A. brown dog
B. roasted carrot
C. frozen ice
D. shiny car

How to use tautology in a sentence

British Dictionary definitions for tautology

/ (tɔːˈtɒlədʒɪ) /

noun plural -gies
the use of words that merely repeat elements of the meaning already conveyed, as in the sentence Will these supplies be adequate enough? in place of Will these supplies be adequate?
logic a statement that is always true, esp a truth-functional expression that takes the value true for all combinations of values of its components, as in either the sun is out or the sun is not outCompare inconsistency (def. 3), contingency (def. 5)

Derived forms of tautology

tautological (ˌtɔːtəˈlɒdʒɪkəl), tautologic or tautologous, adjectivetautologically or tautologously, adverb

Word Origin for tautology

C16: from Late Latin tautologia, from Greek, from tautologos
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012