済 is built from the 氵 (water (left)) and 斉 components.
It reads サイ like 斉, as do 剤 and 斎 — learn 斉 once and the family's reading comes with it.
A common word using 済 is 経済 (けいざい), meaning “economics, finance, economy”.
Don't confuse it with 剤, 斉, and 斎.
