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Ok, so I'm supposed to prepare a short presentation about a grammatical oddity in the English language that doesn't seem correct, and yet it is. The topics range from explaining the plural of fish/fishes to the usage of "none of them are/is brave".

I've decided to touch upon the "don't you dare" phrase, but I'm looking for some clarification of why that structure is in usage, and why can't we say "do not you dare" or "don't she dare" (context-wise likely used as a proxy command/threat).

Anyone care to enlighten me?

marked as duplicate by Scott, Mark Beadles, curiousdannii, Davo, choster Nov 14 '18 at 18:34

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  • 1
    It's purely idiomatic. Grammatically, there is nothing wrong with "Do not you dare." (It means the same thing.) But it would sound so strange to any native speaker that it would not actually be used. – Jason Bassford Nov 12 '18 at 5:19

> […] why can't we say "do not you dare" […]

In present-day English, imperative clauses do not generally include the explicit subject you, except sometimes in colloquial speech. Since don't is relatively colloquial, whereas uncontracted do not is relatively formal, the combination "don't you [imperative]" survives, whereas the combination *"do not you [imperative]" does not. (It wasn't always this way; for example, Shakespeare's Henry IV, Part 1 has "Do not thou, when thou art king, hang a thief", meaning "Do not, when you are king, hang a thief.")

> […] "don't she dare" […]

The subject of an imperative clause is basically always second-person. There are some restricted exceptions — we can say things like "Nobody touch it!" and "Somebody help!" — but something like *"She come here!" is right out. Instead we'd say something like "Have her come here!", or "She'd better come here!", or "She comes here right now, or else!", or whatnot. Likewise, instead of *"Don't she dare!", we'd say (e.g.) "She'd better not dare!"

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