1. (n.) That which is required, or is necessary; something indispensable\.

2. (a.) Required by the nature of things, or by circumstances; so needful that it can not be dispensed with; necessary; indispensable.

appropriate bare necessities boundary condition call for called for catch clause condign condition demand demand for deserved desideration desideratum donnee due escalator clause escape clause escape hatch essential essentials fine print given grounds indicated indispensable irreducible irreductible irreplaceable joker kicker limiting condition merited must must item necessaries necessary necessities necessity need need for needed needful obligation occasion parameter prerequirement prerequisite provision provisions proviso required requirement requisition right rightful saving clause sine qua non small print specification stipulation string suitable terms the necessary the needful ultimatum unforgoable vital want wanted whereas