based on situations or ideas that are possible and imagined rather than real and true (Oxford)
imagined or suggested but not necessarily real or true (Cambridge)
wasn't asking about anybody in particular—it was a purely hypothetical question. (Oxford)
This is all very hypothetical but supposing Jackie got the job, how would that affect you? (Cambridge)
hypothetical question
hypothetical assumption
Imaginary
Speculative
Certain
Definite
Hypothesis
Hypothesize