Noun

1. A condition requiring relief
2. Anything that is necessary but lacking
3. The psychological feature that arouses an organism to action toward a desired goal; the reason for the action; that which gives purpose and direction to behavior
4. A state of extreme poverty or destitution

Verb

1. Require as useful, just, or proper
2. Have need of
3. Have or feel a need for

Adverb

1. In such a manner as could not be otherwise