The strongest incapacity definition: the policy pays if you cannot do your specific job.
Income protection claims are tested against an incapacity definition. Own occupation pays when you cannot perform the material duties of your own job. Weaker alternatives widen the test: suited occupation asks whether you could do any job your education, training or experience fits you for, and any occupation pays only when you cannot work at all. The same medical evidence can pass one definition and fail another, so the definition clause is the first thing to compare between policies — before the premium.