IPA: /ˌsɜːrməˈnɛt/
KK: /sɜrˈmɒnɛt/
A brief speech or talk, often religious in nature, that conveys a moral or spiritual message.
The pastor delivered a sermonette during the Sunday service.
Sermonette → It is formed from "sermon" (from Old French *sermon*, meaning a discourse or speech) and "-ette" (a diminutive suffix meaning small or little). The word "sermonette" refers to a small or brief sermon.
Think of a 'small speech' ('-ette' means little) that is a 'discourse' ('sermon') — that's what a sermonette is.