REASON

noun

1. A cause:
2. Rational thinking (or the capacity for it); the cognitive faculties, collectively, of conception, judgment, deduction and intuition.
3. Something reasonable, in accordance with thought; justice.

verb

1. To deduce or come to a conclusion by being rational
2. To perform a process of deduction or of induction, in order to convince or to confute; to argue.
3. To converse; to compare opinions.