tautology

/tɔˈtɑlədʒi/
noun
  1. The unnecessary repetition of an idea, statement, or word, using different words that mean the same thing.
    • In writing, avoid tautology by not saying 'return back' when 'return' is enough.
    • Saying 'free gift' is a tautology because a gift is already free.
    • The politician's speech was full of tautology, like 'future plans' and 'past history.'
  2. In logic, a statement that is always true because it cannot be false, such as 'either it is raining or it is not raining.'
    • The philosopher argued that the statement 'all bachelors are unmarried' is a tautology.
    • In logic class, we learned that 'A or not A' is a tautology.
    • A tautology in mathematics is a statement that holds true in every possible situation.
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