該 is built from the 言 and 亥 components.
It reads ガイ like 亥, as do 劾 — learn 亥 once and the family's reading comes with it.
A common word using 該 is 該当 (がいとう), meaning “corresponding, answering to, coming under”.
Kanji that look similar include 試, 詩, 詰, and 話.
