Noun

1. A common expression whose wording is not subject to variation.
   • 1951, Gordon M. Messing, "Structuralism and Literary Tradition," Language, vol. 27, no. 1, p. 3:

     Bally remarks in passing, as Hall does not, that the inversion in toujours est-il que is part of a set phrase and hence invariable.

2. A common expression whose words cannot be replaced by synonymous words without compromising the meaning.
   • 1992, Stanislaw Baranczak, "How to Translate Shakespeare's Humor?: (Reflections of a Polish Translator)," Performing Arts Journal, vol. 14, no. 3, p. 83:

     If it proves clearly unfeasible to make the audience laugh at a thin and far-fetched joke, it is always better to change the way the joke works . . . for instance, a pun based on the speaker's taking literally some set phrase or metaphor with a pun based on phonetic similarity.

Usage notes

Specific kinds of set phrase may include: idioms, whose meanings cannot be determined from their parts; proverbs, whose meanings can be derived from their parts and which express practical wisdom and often take the form of complete sentences; and catchphrases, set phrases associated with a specific person or group. Most idioms and proverbs are not set phrases, however, as significant variation is often possible. Also many idiomatic expressions do not form single units but allow intervening terms.

Set phrases are often clichés or colloquialisms, but these terms may include expressions other than set phrases.

See also

• catchphrase
• cliché, cliche
• colloquialism
• fixed expression
• idiom
• proverb