Is he an stupid or is he a stupid?

In the wording you have (Is he...), you would simply write "Is he stupid."
But, if there is a descriptive word after the word "stupid", ONLY then would you write, "a stupid". For example: "Is he a stupid oaf."

You can't say "an stupid" because the word stupid does not begin with a vowel sound and "an" is only used before words with a vowel at beginning. BUT that rule does not apply with proper names, for example, it would be incorrect to write:

Incorrect: Orrin is an stupid.
Correct: Orrin is stupid.

HOWEVER, "stupid" is derogatory and name-calling when used about a person! Stupid is also a "value judgement", in which one person judges another. It is mere opinion, not fact. So try to pick a different word.


Incorrect: Julie thought that was an stupid book.
Correct: Julie thought that was a stupid book.


Typically, in the English language, there would rarely be a time that it would be correct to write "an stupid". In almost all cases, the wording will be "a stupid" or simply "stupid" (without "a" before it).