Thus we say: You never know, which is why. but You never know. That is why.
Understanding the Context
And goes on to explain: There is a subtle but important difference between the use of that and which in a. Feb 12, 2018 · In the sentence "Why is this here?", is "why" an adverb? What part of speech is "why?" I think it modifies the verb "is", so I think it is an adverb.
