motivation, motive, need - 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; "we did not understand his motivation"; "he acted with the best of motives"

reason, ground - a rational motive for a belief or action; "the reason that war was declared"; "the grounds for their declaration"

incentive, inducement, motivator - a positive motivational influence

deterrence, disincentive - a negative motivational influence