need—noun

1. a requirement, necessary duty, or obligation: There is no need for you to go there.
2. a lack of something wanted or deemed necessary: to fulfill the needs of the assignment.
3. urgent want, as of something requisite: He has no need of your charity.
4. necessity arising from the circumstances of a situation or case: There is no need to worry.
5. a situation or time of difficulty; exigency: to help a friend in need; to be a friend in need.
6. a condition marked by the lack of something requisite: the need for leadership.
7. destitution; extreme poverty: The family’s need is acute.

—verb (used with object)

8. to have need of; require: to need money.

—verb (used without object)

9. to be under an obligation (used as an auxiliary, typically in an interrogative or in a negative statement, and followed by infinitive, in certain cases without to; in the 3d person singular the form is need, not needs): He need not go.
10. to be in need or want.
11. to be necessary: There needs no apology.

—Idioms

12. if need be,should the necessity arise: If need be, I can type the letters myself.

Origin: before 900; (noun) Middle English nede, Old English nēd (WSaxon nīed), cognate with German Not, Old Norse nauth, Gothic nauths; (v.) Middle English neden, Old English nēodian, derivative of the noun

—Related forms
need·er, noun
un·need·ed, adjective
well-need·ed, adjective

—Synonyms
3. requirement. 5. emergency. 7. neediness, indigence, penury, privation. 8. want, lack.

—Synstudy
2, 3. See lack. 4. Need, necessity imply a want, a lack, or a demand, which must be filled. Need, a word of Old English origin, has connotations that make it strong in emotional appeal: the need to be appreciated. Necessity, a word of Latin origin, is more formal and impersonal or objective; though much stronger than need in expressing urgency or imperative demand, it is less effective in appealing to the emotions: Water is a necessity for living things. 7. See poverty.

—Antonyms
7. wealth.