1. statements that are true by definition or logical necessity, often considered redundant or circular
Usage: logic; philosophy
2. needless repetition of an idea in different words
Usage: rhetoric; writing

Examples

• The professor explained that tautologies like ‘all bachelors are unmarried men’ are logically true but uninformative.
• His speech was full of tautologies that added nothing to his argument.
• In logic class, we learned to identify tautologies and distinguish them from meaningful propositions.
• The writer’s editor removed several tautologies to make the text more concise.
• Mathematical tautologies are always true regardless of the values of their variables.
• She criticized the politician’s use of tautologies instead of substantive policy details.