IPA: /kəmˈpleɪnt/
KK: /kəmˈpleɪnt/
A statement or expression of dissatisfaction or unhappiness about something.
She filed a complaint about the poor service at the restaurant.
Complaint → It is formed from "com-" (meaning together) and "plangere" (meaning to strike or lament). The word refers to expressing dissatisfaction or lamenting about a situation together with others.
Think of people coming together ('com-') to express their dissatisfaction or 'lament' ('plangere') about something — that's what a complaint is.