IPA: //ˈɡeɪn.fəl//
KK: /ˈɡeɪnfl/
Something that provides profit or benefit, often related to work or employment.
She found a gainful job that allowed her to support her family.
Gainful → It is formed from "gain" (from Old French *gaigne*, meaning profit or advantage) and "-ful" (meaning full of). The word "gainful" means full of gain or providing profit.
Think of 'gain' as something that brings you profit, and '-ful' means full of it. So, gainful means full of profit.