IPA: /ˌæpərˈteɪn/
KK: /æpərˈteɪn/
To belong to or be connected with something as a proper part or function.
The rules that appertain to this game are very strict.
Past: appertained
Past Participle: appertained
Appertain is formed from "ad-" (meaning to or towards) and "pertain" (from Latin "pertinere", meaning to belong or relate). The word describes something that belongs or is related to a particular subject or matter.
Think of something that 'belongs to' or 'relates to' a specific topic — 'ad-' means towards, and 'pertain' means to belong.