I think I know why everyone's weird; they are all engineers!
Why is it wrong if I miss a or an?
Hmm, is هَل like an interrogative marker, or does it literally mean "is"?
هَل is an interrogative marker. Adding هَل at the beginning of a sentence makes it a yes/no question about the sentence.
But when you tap to see what's mean it says "does" the meaning of هل