IPA: /ˈpleɪnˌtʃænt/
KK: /plɛnˌtʃænt/
A type of unaccompanied sacred song used in the Christian church, characterized by a single melodic line and free rhythm.
The choir performed a beautiful plainchant during the service.
Plainchant → It is formed from "plain" (from Old French *plain*, meaning flat or simple) and "chant" (from Latin *cantare*, meaning to sing). The word "plainchant" refers to a simple, unadorned style of singing, typically associated with medieval church music.
Think of 'plain' meaning simple or flat, and 'chant' meaning to sing. This helps you remember that plainchant is a simple style of singing.