The definition of a need is a desire or requirement.(noun)
Need is defined as to want, desire or require.(verb)
See need in Webster's New World College Dictionary
Origin: ME nede < OE nied, akin to Ger not, Goth nauths < IE *neuti- < base *neu-, to collapse with weariness > Welsh newyn, starvation
See need in American Heritage Dictionary 4
Origin: Middle English nede
Origin: , from Old English nēod, nēd, distress, necessity. Usage Note: Depending on the sense, the verb need behaves sometimes like an auxiliary verb (such as can or may) and sometimes like a main verb (such as want or try). When used as a main verb, need agrees with its subject, takes to before the verb following it, and combines with do in questions, negations, and certain other constructions: He needs to go. Does he need to go so soon? He doesn't need to go. When used as an auxiliary verb, need does not agree with its subject, does not take to before the verb following it, and does not combine with do: He needn't go. Need he go so soon? The auxiliary forms of need are used primarily in present-tense questions, negations, and conditional clauses. Unlike can and may, auxiliary need has no form for the past tense like could and might.Regional Note: When need is used as the main verb, it can be followed by a present participle, as in The car needs washing, or by to be plus a past participle, as in The car needs to be washed. However, in some areas of the United States, especially western Pennsylvania and eastern Ohio, many speakers omit to be and use just the past participle form, as in The car needs washed. This use of need with past participles is slightly more common in the British Isles, being particularly prevalent in Scotland.
Learn more about need