Thus we say: You never know, which is why... but You never know. That is why... And goes on to explain: There is a subtle but important difference between the use of that and which in a sentence, and it has to do primarily with relevance. Grammarians often use the terms "restrictive" and "non-restrictive" when it comes to relative clauses.
"why" can be compared to an old Latin form qui, an ablative form, meaning how. Today "why" is used as a question word to ask the reason or purpose of something.
8 1) Please tell me why is it like that. [grammatically incorrect unless the punctuation is changed. Please tell me: Why is it like that? The question: "Why is [etc.]" is a question form in English: Why is the sky blue? Why is it that children require so much attention? Why is it [or some thing] like that?
Good explanation of why it's optional in this case, although I'm not convinced that reason is the only reasonable antecedent of why. For example, the explanation why is a common usage, and I don't think you can freely substitute that in that case either. (Perhaps it's already a contraction of the explanation of why?)
Since we can say "Why can we grow taller?", "Why cannot we grow taller?" is a logical and properly written negative. We don't say "Why we can grow taller?" so the construct should not be "Why we cannot grow taller?" The reason is that auxiliaries should come before the subject to make an interrogative.
The question is: why did the English adapt the name pineapple from Spanish (which originally meant pinecone in English) while most European countries eventually adapted the name ananas, which came from the Tupi word nanas (also meaning pineapple).
Why don't these words fit the pattern of thirteen through nineteen? [Answer to 1] A remarkably thorough answer to (1) appears at Why do eleven and twelve get unique words and not end in "-teen"? .