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.

the repetitious or unnecessary use of words that do not provide new information in an utterance, as Hear, hear! or I myself said... Note: Tautologies occur commonly in everyday speech. adj. tautologous.

the saying of the same thing twice over in different words a statement in which the predicate asserts no more than is contained in the meaning of the subject an instance of a valid formula of propositional logic a complex proposition which is true independently of the truth values of its constituent atomic propositions a statement that is necessarily true an analytic statement see also: propositional tautology

the saying of the same thing twice over in different words, esp. as a fault of style

(logic) a statement that is necessarily true; "the statement `he is brave or he is not brave' is a tautology"

useless repetition; "to say that something is `adequate enough' is a tautology"

a Boolean expression E which evaluates to true no matter what Boolean values are given to the variables appearing in E

a case which is true by definition

a formula that is true in every interpretation, contingent if true on some interpretation, and contradictory if false on every interpretation

a logical statement in which the conclusion is equivalent to the premise

a meaningless repetition of the same idea in different words

a propositional formula that is true regardless of the values of the atomic propositions

a proposition that is always true

a proposition which conveys no real information because it is necessarily true

a redundancy, the unnecessary repetition or duplication of a word or an idea

a repetition of the meaning of a statement, using different words or symbols

a repetitive, true statement, or sometimes circular reasoning

a scientific logical truth and proof, in and of itself

a special case of what we might call analytic statements

a statement that includes all possibilities and is therefore useless

a statement that is always true

a statement that is necessarily true (i

a statement that is true in virtue of the meaning of the logical connectives present in the statement

a statement that purports to prove something, but does nothing more than restate the premise in a different form

a statement which is always true

a statement which is necessarily true because it cannot be used to make a false assertion by virtue of its logical form

a statement which is necessarily true, true by definition, and true under any conditions

a statement which is technically true, but which says nothing of substance

a statement whose truth table outcome is always T

An analytic proposition that is necessarily true or self-evident, but which gives no useful information, i.e., "It will rain tomorrow or it will not rain tomorrow."

The unnecessary and excessive repetition of the same idea in different words in the same sentence, as "the room was completely dark and had no illumination," or "a breeze greeted the dusk and nightfall was heralded by a gentle wind." (Compare Pleonasm)

An expression is a tautology if every interpretation of it is a model of the expression. Tautologies evaluate to True under all of their interpretations.

Unnecessary repetition. For example: I have been all on my own by myself for hours.

In propositional logic, a tautology (from the Greek word Ï„Î±Ï…Ï„Î¿Î»Î¿Î³Î¯Î±) is a statement that is truth-functionally valid—i.e. it is universally true, or true in every interpretation (or model or valuation). For example, the statement "If it rains, then it rains" is a tautology. Every theorem of propositional logic is a tautology, and so we can equivalently define 'tautology' as any theorem of propositional logic—i.e. any statement that is deducible from the empty set in some system of deduction of propositional logic, such as a natural deduction system.