(now rare) Having the faculty of reason; rational, reasoning. / Just; fair; agreeable to reason. / Not excessive or immoderate; within due limits; proper. / Not expensive; fairly priced. / Satisfactory.

(uncountable) The state or characteristic of being reasonable. / (countable) A reasonable action or behaviour.

plural of reasonableness

The state or quality of being reasonable; reasonableness.

plural of reasoning

One who reasons.

plural of reasoner

based on reasoning; being the result of logical thought

simple past tense and past participle of reason

That which causes something: an efficient cause, a proximate cause. / A motive for an action or a determination.