English Idioms

What is an Idiom?
There are two features that identify an idiom: firstly, we cannot deduce the meaning of the idiom from the individual words; and secondly, both the grammar and the vocabulary of the idiom are fixed, and if we change them we lose the meaning of the idiom. Thus the idiom "pull your socks up" means "improve the way you are behaving" (or it can have a literal meaning); if we change it grammatically to "pull your sock up" or we change its vocabulary to "pull your stockings up", then we must interpret the phrase literally - it has lost its idiomatic meaning.
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