A need is something that is necessary for an organism to live a healthy life. Needs are distinguished from wants in that, in the case of a need, a deficiency causes a clear adverse outcome: a dysfunction or death.
Needs can be objective and physical, such as the need for food, or psychological and subjective, such as the need for self-esteem.
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