n.
In psychology, an urgent need pressing for satisfaction, usually rooted in some physiological deficiency or imbalance (e.g., hunger and thirst) and impelling the organism to action.
Psychologists distinguish between drives that are innate and directly related to basic physiological needs (e.g., food, air, and water) and drives that are learned (e.g., drug addiction). Among the other drives psychologists have identified are achievement, affection, affiliation, exploration, manipulation, maternity, pain avoidance, sex, and sleep.