tautology

Tautology is useless restatement, or saying the same thing twice using different words. “Speedy sprint" is a tautology because sprint already means "speedy running."

The noun tautology originates from the Greek word tautologos, meaning “repeating what is said.” "A pedestrian traveling on foot" is a tautology because a pedestrian, by definition, is someone who walks. In the study of logic, a tautology is a statement that is necessarily true under any interpretation and cannot be denied without introducing logical inconsistencies. "It will snow tomorrow, or it will not snow tomorrow" is an example. No argument here — it's true any way you look at it.

Definitions of tautology
  1. noun
    useless repetition
    “to say that something is `adequate enough' is a tautology
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    type of:
    repetitiousness, repetitiveness
    verboseness resulting from excessive repetitions
  2. noun
    (logic) a statement that is necessarily true
    “the statement `he is brave or he is not brave' is a tautology
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    type of:
    true statement, truth
    a true statement
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