"No" is not ever a complete sentence, regardless of its punctuation. I really wish this would go away, but it keeps popping up in recovery circles and whatnot, so I'm going to vent.
In order to be a complete sentence, one must have in play a subject and a verb.
Sentences like
"Go." and
"Be."
are complete, as the second person subject (you) is understood; "go" and "be" are the correct conjugations of the verbs.
"No" is not a verb.
"No" is not a sentence with or without the period at the end.
"No." /is/ a complete answer. If you are asked to do something, it is not necessary for you to justify or explain why you cannot or do not want to do this thing; if that person wishes, he or she is free to ask why.
You are also free to say "No." to their request for additional information.
But no, "No." is not a complete sentence, and it is ignorant to say otherwise. That's 3rd grade grammar ^__^
It lacks a subject and a verb. It is not in any sense a complete sentence.
However "I will not." Is, and serves much the same function.
ps/smoh
