requirement, demand -- (required activity; "the requirements of his work affected his health"; "there were many demands on his time")
necessity, essential, requirement, requisite, necessary -- (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")
prerequisite, requirement -- (something that is required in advance; "Latin was a prerequisite for admission")
(Sound)
