I know a relative adverb "why" can be followed by a clause and make the clause a noun phrase. It can play a role as an object or a subject in another sentence.

For example)

I know the reason why she is still single.

Sometimes, the antecedent is okay to be dropped, if readers can guess there has to be the antecedent "the reason" with the context.

I know (the reason) why she is still single.

Likewise, the under-written sentence is possible.

The reason why she is still single is because she is ugly.

However no native speaker says like this:

(The reason) Why she is still single is because she is ugly.

Wrong??? Why? Is there any specific reason?

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    We might say "Why she is single is a mystery" but not usually the inversion you are asking about. Jan 18, 2021 at 16:47
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    @WeatherVane Would a native speaker ever say something like “Why he’s still confused is because no-one explained it well.”? I think we would drop the “why” as well “the reason”, “He’s still confused because...”
    – ColleenV
    Jan 18, 2021 at 16:57
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    @ColleenV: Well, that's a somewhat different usage. Strictly speaking, I'd say a "why- clause* is a kind of noun (in contexts where it's completely interchangeable with the reason why... - also a noun phrase). And the normal syntax is The reason IS [some statement, a "tensed" clause]*. Where that "statement" is often preceded by the word because. But usage is obviously changing a lot in this area right now - witness people saying things like She's single because ugly, and Irregular verbs are hard to learn because English. Jan 18, 2021 at 19:07
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    But now I got it and I realized why you are talking about "because". According to Practical English Usage, 567. Reason In an informal style, why/that is often left out. The reason she doesn't like me is that I make her nervous. 『Some people consider it incorrect to use a because-clause as a complement after reason (as in Sorry I'm late - the reason is because I overslept).』 Jan 19, 2021 at 15:51
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    @KateBunting As well, I've got to know certain condition to allow the reason to be omitted. the place where ..the day when ..the reason why ... 『The place, the day or the reason can be dropped in an informal style, especially in the middle of a sentence.... Spain's where we're going this year. Why I'm here is to talk about my plans. (More formal: The reason why I'm here is...)』 Jan 19, 2021 at 15:55

1 Answer 1


You make a mistake in your reasoning with this sentence:

I know (the reason) why she is still single.

That is not actually the sentence here that is being shortened. Nothing is being shortned. Compare:

I know why... I know what... I know who... I know where... I know which...

In none of these examples would we be thinking "I know (the thing) what ..." "I know the place where..."

In each of these 'why', 'what', 'who' are acting as pronouns all by themselves. Native English speakers could ask, for example, "Did you ever get 'the why'?" meaning "Did he ever tell you why this is happening/going to happen?"

  • Hi. I have seen the possible cases to drop (the reason, the place, the time) regarding relative adverbs in Practical English Usage and other learning materials. Jan 21, 2021 at 6:09

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