1. (n.) The act of requiring; demand; requisition.

2. (n.) That which is required; an imperative or authoritative command; an essential condition; something needed or necessary; a need.

bare necessities blackmail call call for claim condition contribution demand demand for desideration desideratum draft drain duty essential essentials exaction extortion extortionate demand heavy demand imposition impost indent indispensable insistent demand levy must must item necessaries necessities necessity need need for nonnegotiable demand notice occasion order precondition prerequirement prerequisite provision proviso qualification requisite requisition rush rush order sine qua non stipulation tax taxing the necessary the needful tribute ultimatum want warning