reason · ​. [countable] a cause or an explanation for something that has happened or that somebody has done · ​. [uncountable] a fact that makes it right or fair ...

1[countable] a cause or an explanation for something that has happened or that someone has done reason (why…) · 2[uncountable] a fact that makes it right or fair ...

​[transitive, intransitive] reason (that…) | + speech to form a judgement about a situation by considering the facts and using your power to think in a logical ...

+ speech to form a judgment about a situation by considering the facts and using your power to think in a logical way She reasoned that she must have left her ...

There is one meaning in OED's entry for the noun reason. See 'Meaning & use' for definition, usage, and quotation evidence. This word is now obsolete.

phrasal verb. reason with somebody. ​to talk to somebody in order to persuade them to be more sensible. I tried to reason with him, but he wouldn't listen.

to talk to someone in order to persuade them to be more sensible. I tried to reason with him, but he wouldn't listen.

There are 17 meanings listed in OED's entry for the verb reason, six of which are labelled obsolete. See 'Meaning & use' for definitions, usage, and quotation ...

(of an argument, opinion, etc.) presented in a logical way that shows careful thought. His claims were supported with proofs and reasoned argument.

reason noun (JUDGMENT) ... the ability to think and make judgments, esp. good judgments: Meditation seemed to have improved her ability to reason.