tautology

From Late Latin tautologia, from Ancient Greek ταυτολογία (tautología) from ταὐτός (tautós, “the same”) + λόγος (lógos, “explanation”)

• (UK) IPA^(key): /tɔˈtɒl.ə.d͡ʒi/
• (General American) IPA^(key): /tɔˈtɑl.ə.d͡ʒi/
• Rhymes: -ɒlədʒi

tautology (countable and uncountable, plural tautologies)

1. (uncountable) Redundant use of words, a pleonasm, an unnecessary and tedious repetition.

   It is tautology to say, "Forward Planning".

2. (countable) An expression that features tautology.

   The expression "raze to the ground" is a tautology, since the word "raze" includes the notion "to the ground".

   • 1946, Bertrand Russell, History of Western Philosophy:

     Pure mathematics consists of tautologies, analogous to ‘men are men’, but usually more complicated.

3. (countable, logic) In propositional logic: a statement that is true for all truth values of its propositional variables. In first-order logic: a statement that is true for all truth values of its Boolean atoms.

• (linguistics: expression): contradiction in terms
• (in logic): contradiction
• (literary): oxymoron

• (in logic): contingency, contradiction

• pleonasm
• redundancy
• Tautology on Wikipedia.Wikipedia