reason

(noun): A cause:
(noun): Rational thinking (or the capacity for it); the cognitive faculties, collectively, of conception, judgment, deduction and intuition.
(noun): Something reasonable, in accordance with thought; justice.
(noun): Ratio; proportion.
(verb): To deduce or come to a conclusion by being rational
(verb): To perform a process of deduction or of induction, in order to convince or to confute; to argue.
(verb): To converse; to compare opinions.
(verb): To arrange and present the reasons for or against; to examine or discuss by arguments; to debate or discuss.
(verb): To support with reasons, as a request.
(verb): To persuade by reasoning or argument.
(verb): (with down) To overcome or conquer by adducing reasons.
(verb): (usually with out) To find by logical process; to explain or justify by reason or argument.