In linguistics, a redundancy is information that is expressed more than once.
Examples of redundancies include multiple agreement features in morphology,
Redundancy versus repetition
Writing guides, especially for technical writing, usually advise avoiding redundancy, "especially the use of two expressions that mean the same thing. Such repetition works against readability and conciseness." Others make a distinction between redundancy and repetition:
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Repetition, if used well, can be a good tool to use in your writing. It can add emphasis to what you are trying to say and strengthen a point. There are many types of useful repetition. Redundancy, on the other hand, cannot be a good thing. Redundancy happens when the repetition of a word or idea does not add anything to the previous usage; it just restates what has already been said, takes up space, and gets in the way without adding meaning.
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Computer scientist Donald E. Knuth, author of highly acclaimed textbooks, recommends "to state things twice, in complementary ways, especially when giving a definition. This reinforces the reader's understanding."
See also
- Bilingual tautological expressions
- Redundancy - information that is expressed more than once