Multiple questions herein ask "Is it grammatically correct to begin a sentence or question with X?"
So, I'm definitively asking, are there any words for which it is absolutely not grammatically correct to begin a sentence with?
I am not looking for a list, and I'm not (effectively) looking for a class of words, though that may be evident if a specific word is presented, but only as a part of
_____ is an example, and words like _____.
I am not looking for discussion, either. I would assume the answer is No, you may grammatically start a sentence with any word. but would like to be proven incorrect.
Than any other question, this one should actually have an answer.
Also, no quotation mark tricks or the like. The word should have grammatical context and retain its own definition in place. Filling in the example also does not count for the answer. (Use, not mention).
The word should itself be grammatically acceptable. If ain't is not grammatically acceptable, then it ain't allowed as a word in this context.