1 : a fact that logically justifies some premise or conclusion
2 : an explanation of the cause of some phenomenon
3 : a fact or assertion offered as evidence that something is true
4 : a rational motive for a belief or action
5 : 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
6 : a justification for something existing or happening
