Requirements

n. something that is demanded; necessity, something that is needed

This article is about engineering. For other kinds of requirements, see Need.In engineering, a 'requirement is a singular documented need of what a particular product or service should be or do. It is most commonly used in a formal sense in systems engineering or software engineering. It is a statement that identifies a necessary attribute, capability, characteristic, or quality of a system in order for it to have value and utility to a user.
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Noun
1. required activity; "the requirements of his work affected his health"; "there were many demands on his time"
(synonym) demand
(hypernym) duty, responsibility, obligation
(derivation) necessitate, ask, postulate, need, require, take, involve, call for, demand
2. 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"
(synonym) necessity, essential, requisite, necessary
(hypernym) thing
(hyponym) desideratum
(derivation) want, need, require
3. something that is required in advance; "Latin was a prerequisite for admission"
(synonym) prerequisite
(hypernym) duty, responsibility, obligation
(hyponym) precondition

<programming> The first stage of software development which defines what the potential users want the system to do. In modern methods these requirements should be testable, and will usually be traceable in later development stages. A common feature of nearly all software is that the requirements change during its lifetime.
See software life-cycle.
(1995-11-11)

The ability of an item to perform a required function under stated conditions for a stated period of time.