necessary (
http://definr.com/necessary)
adj 1: absolutely essential [ant:
unnecessary]
2: unavoidably determined by prior circumstances; "the
necessary consequences of one's actions"
n : anything indispensable; "food and shelter are necessities of
life"; "the essentials of the good life"; "allow farmers
to buy their requirements under favorable conditions"; "a
place where the requisites of water fuel and fodder can
be obtained" [syn:
necessity,
essential,
requirement,
requisite] [ant:
inessential]