Find a Research Gap
A gap is only real if you can show where the work ends. See the papers that mark that edge.
A research gap is not an absence you assert; it is one you can show. "Nobody has studied X" is a claim a reviewer will test in one search, and it fails more often than people expect — usually because the work exists under different terminology, in an adjacent field, or in a language the searcher does not read. A defensible gap statement names what has been done, where it stops, and why the stopping point matters. That means the useful output is not "here is a gap" but the papers that mark the edge of the current literature, which is what you will have to cite when you make the claim.
How do I know a gap is real?
By finding the papers closest to it. A gap you can only assert is a gap a reviewer will close with one search.
What if the work exists in another field?
Then it is not a gap, but a bridge — and framing it as a translation between fields is usually a stronger contribution than claiming novelty.
Is a gap enough to justify a study?
No. Plenty of things are unstudied because nobody needs the answer. The gap has to matter to someone for a reason you can state.