sentence structure for questions

[4ntoni4]

what kind of sentence structure would a quesion like 'what is your favourite hobby?' be?? or would it be considered a phrase

[EulerFan102]

Hey, great question! 

So, the structure of a sentence depends solely on the verb phrases in a sentence. If a sentence has only one verb phrase, then it will be a simple sentence. The sentence "What is your favourite hobby?" has just the one verb phrase ("is"), so it's a simple sentence.
(and no, it wouldn't be considered a phrase. They're smaller components within sentences.)

The reason it may feel a bit weird to label this as a simple sentence is due to the strange way that the English language forms questions. If the question involves a "what", "where", "who" etc., then it's standard for that pronoun to be at the start of the sentence, requiring reordering of the sentence. We can compare the question's structure to that of a possible answer, like "My favourite hobby is unicycling" or "Unicycling is my favourite hobby". These have very similar structures to the question but it feels more natural to label them as simple sentences, as there's no longer that reordering to put the "what" first.