Is it an idiot or a idiot?

Answer 1

An idiot. The English "article of speech", "an", must be used before a word beginning with a vowel and some specific words beginning with a consonant.

Correct: a duck

Correct: an alligator

A and an refer to some unspecific object, person, animal. The "article" "the" is used for a specific object, person, animal.

Correct: I saw an alligator!

Correct: The alligator attacked me! (If you know which exact alligator attacked.)

Correct: An alligator attacked me! (If you do not know which one did it.)

Answer 2

The correct article to use before the word "idiot" is "an." This is because the word "idiot" begins with a vowel sound, specifically the sound /ˈaɪdiət/. When determining which article to use, it is important to consider the sound that the word starts with, rather than the actual letter.