noun

- The statement "the reason is because" is an example of a tautology because "the reason" and "because" are essentially the same thing said twice in different ways.
- The statement "it is either right or it is left" is an example of a tautology because the statement by definition always has to be true.

The definition of a tautology is a statement that says the same thing twice in different ways, or a statement that has to be true by the way it is phrased.

## tautology

*pl.* -·gies

- needless repetition of an idea in different words; redundancy; pleonasm (Ex.: “necessary essentials”)
- an instance of such repetition

- Logic a proposition that is analytic (sense )

Origin of tautology

Late Latin*tautologia*; from Gr: see tauto- and amp; -logy

## tautology

noun

*pl.*

**tau·tol·o·gies**

**a.**Needless repetition of the same sense in different words; redundancy.**b.**An instance of such repetition.-
*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.*

Origin of tautology

Late Latin*tautologia*, from Greek

*tautologia*, from

*tautologos*,

*redundant*:

*tauto-*,

*tauto-*+

*logos*,

*saying*; see

**–logy**.

*Related Forms:*

**tau′to·log′i·cal**,**tau′to·log′ic**,**tau·tol′o·gous**adjective

**tau′to·log′i·cal·ly**,**tau·tol′o·gous·ly**adverb

## tautology

Noun

(*countable and uncountable*, *plural* tautologies)

- (uncountable) redundant use of words
*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".*

- (countable, logic) A statement that is true for all values of its variables
*Given a Boolean A, "A OR (NOT A)" is a tautology.**A logical statement which is neither a tautology nor a contradiction is a contingency.**A tautology can be verified by constructing a truth tree for its negation: if all of the leaf nodes of such truth tree end in X's, then the original (pre-negated) formula is a tautology.*

Origin

From Late Latin *tautologia*, from Ancient Greek *Ï„Î±Ï…Ï„Î¿Î»Î¿Î³Î¯Î±* (tautologÃa) from *Ï„Î±á½Ï„ÏŒÏ‚* (tautÃ³s, “the same") + *Î»ÏŒÎ³Î¿Ï‚* (lÃ³gos, “explanation")