IPA: //ˈpriːpeɪmənt//
KK: /priˈpeɪmənt/
A payment made before it is due or before receiving a service or product.
The company requires a prepayment before starting the project.
Prepayment → It is formed from "pre-" (meaning before) and "payment" (from Old French *paiment*, meaning the act of paying). The word "prepayment" refers to the act of paying before a service or product is received.
Think of paying 'before' ('pre-') receiving something, which is what prepayment means.