In classical discussions, māhiyyah often answers “what is it?”; ḥaqīqah concerns a thing's real nature; huwiyyah can stress particular identity or that-which-it-is. Exact usage varies by context.
Different analytical considerations do not require three separately existing objects. They may be ways of examining one and the same thing.
“What is a human?”, “Who is this person?”, and “Does this person exist outside thought?” pose different questions that must not be collapsed.