tautology

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Tautology (logic)

From Late Latin tautologia, from Ancient Greek ταὐτολογία (tautología) from ταὐτός (tautós, “the same”) + λόγος (lógos, “explanation”). By surface analysis, tauto- +‎ -logy.

tautology (countable and uncountable, plural tautologies)

(uncountable) Redundant use of words, a pleonasm, an unnecessary and tedious repetition.
It is tautology to say, "Forward Planning".
(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.
(countable, logic, propositional logic) A statement that is true for all truth values of its propositional variables.
(countable, logic, first-order logic) A statement that is true for all truth values of its Boolean atoms.

terms derived from tautology (noun)

uncountable: redundant use of words

expression that features tautology

Chinese: 套套邏輯 / 套套逻辑 (zh), 套套逻辑 (zh) (tàotàoluóji); 廢話 / 废话 (zh) (fèihuà), 废话 (zh) (fèihuà)
Danish: tautologi c
Dutch: tautologie (nl) f
Finnish: tautologia (fi), toisto (fi)
French: tautologie (fr) f, lapalissade (fr) f, pléonasme (fr) m, truisme (fr) m
German: Tautologie (de) f
Greek: ταυτολογία (el) f (taftología)
Hungarian: tautológia (hu)
Italian: tautologia (it) f
Japanese: 同語反復 (ja) (どうごはんぷく, dōgo hanpuku), トートロジー (ja) (tōtorojī)
Macedonian: тавтологија f (tavtologija)
Portuguese: redundância (pt) f, pleonasmo (pt) m, tautologia (pt) f
Romanian: tautologie (ro) f, pleonasm (ro) n
Serbo-Croatian: tautologija (sh) f
Spanish: redundancia (es) f, pleonasmo (es) m, tautología (es) f (rhetoric)
Swedish: tautologi (sv) c
Ukrainian: тавтоло́гія f (tavtolóhija)

in logic

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