0
"Why?" is not a sentence, because It does not have either a subject or verb. It is acceptable only for informal usage.
The general rule in English is that a sentence may imply either a subject or a verb, but not both. As others have suggested, "Go!" can qualify as a sentence. The subject (you, the listener) is implied, but the verb, "go," is stated. So it can be a sentence. Another sentence of the same type is, "You!" which means, "You are the one." In this example the subject, "you," is stated, so the sentence only has to imply the verb, "are."
With "Why?" however, both the subject and the verb are implied. When written by itself, "why?" usually means either, "Why should I do that?" or "Why do you think that?" Those have subjects and verbs (I and do, or you and think). Since both have to be implied here, "Why?" by itself, is acceptable only in speech and in informal writing.
What else can I help you with?
Is who a sentence?
As a question, it can be a sentence, like: A sentence can have one word, and as a question then it can be a sentence: Who?
Is what a sentence?
A "sentence" in grammar is a group of words that expresses a complete thought. Most sentences consist of at least a subject (noun form) and a predicate (verb form). The word "sentence" can also mean the punishment given for a criminal offense. Specifically, a sentence may include incarceration, or fines, or both, and may contain a period of supervised probation.
Can you give a sentence with the word question?
Generally one should not answer a question with a question.
When do you capitalize a one word answer to a question?
You should capitalize a one-word answer to a question when that word would normally be capitalized in a sentence, such as for proper nouns or the pronoun "I." Otherwise, no additional capitalization is needed for one-word answers.
Can you put the word hears in a question sentence?
no one hears that word anymore
How do you write escaping as a sentence?
As a one-word answer to the question, "What are you doing?".
How do you use the word repeat in a sentence?
An example of using the word repeat in a sentence is " Can you repeat that question one more time? "
What is one sentence that involds the word enthusiastally?
"They discussed the question enthusiastically"
Can you give me a sentence using the word but?
I was looking for a question but I was distracted by this one.
Can you give me a sentence with the word thirteen in it?
your question could count as one
Can you give me a sentence for the word why?
The sentence with the word 'why': Why do you ask this question?
What is a interagative sentence?
An interrogative sentence is one that asks a question. Do you understand? That is an interrogative sentence. Comes from word interrogate, to ask.
