From The Art and Popular Culture Encyclopedia
A set phrase or fixed phrase is a phrase whose parts are fixed, even if the phrase could be changed without harming the literal meaning. This is because a set phrase is a culturally accepted phrase. A set phrase does not necessarily have any literal meaning in and of itself. Set phrases may function as idioms (e.g. red herring) or as words with a unique referent (e.g. Red Sea).
Examples of set phrases
Some set phrases are used as either their own statement or as part of a longer statement:
- I see - Can be used both metaphorically and literally.
- I don't know
- Thank you - There is an implied "I" that is almost never used with the set phrase.
- You're welcome - Note that while 'You are welcome' would have the same literal meaning, it is very rarely used in the same way.
Others are almost always used with more detail added:
- Don't look now... - Used either literally or figuratively to warn someone about an imminent misfortune.
- You know... - Usually used rhetorically to make the audience think about the following topic.