from The American Heritage® Dictionary of the English Language, 4th Edition

  • n. Needless repetition of the same sense in different words; redundancy.
  • n. An instance of such repetition.
  • n. Logic An empty or vacuous statement composed of simpler statements in a fashion that makes it logically true whether the simpler statements are factually true or false; for example, the statement Either it will rain tomorrow or it will not rain tomorrow.

from Wiktionary, Creative Commons Attribution/Share-Alike License

  • n. redundant use of words
  • n. An expression that features tautology.
  • n. A statement that is true for all values of its variables

from the GNU version of the Collaborative International Dictionary of English

  • n. A repetition of the same meaning in different words; needless repetition of an idea in different words or phrases; a representation of anything as the cause, condition, or consequence of itself, as in the following lines: -- The dawn is overcast, the morning lowers, And heavily in clouds brings on the day. Addison.

from The Century Dictionary and Cyclopedia

  • n. Repetition of the same word, or use of several words conveying the same idea, in the same immediate context. See dilogy.
  • n. The repetition of the same thing in different words; the useless repetition of the same idea or meaning: as, “they did it successively one after the other”; “both simultaneously made their appearance at one and the same time.”
  • n. Synonyms Redundancy, etc. See pleonasm.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • n. (logic) a statement that is necessarily true
  • n. useless repetition


Late Latin tautologia, from Greek tautologiā, from tautologos, redundant : tauto-, tauto- + logos, saying; see -logy.
(American Heritage® Dictionary of the English Language, Fourth Edition)
From Late Latin tautologia, from Ancient Greek ταυτολογία (tautología) from ταὐτός (tautós, "the same") + λόγος (lógos, "explanation") (Wiktionary)



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