reason

n. 1 motive, cause, or justification. 2 fact adduced or serving as this. 3 intellectual faculty by which conclusions are drawn from premisses. 4 sanity (lost his reason). 5 sense; sensible conduct; what is right, practical, or practicable; moderation. v. 1 form or try to reach conclusions by connected thought. 2 (foll. By with) use argument with (a person) by way of persuasion. 3 (foll. By that) conclude or assert in argument. 4 (foll. By into, out of) persuade or move by argument. 5 (foll. By out) think out (consequences etc.). 6 (often as reasoned adj.) Express in a logical way. 7 embody reason in (an amendment etc.).  by reason of owing to. In (or within) reason within the bounds of moderation. With reason justifiably. [latin ratio]

n. A thought or a consideration offered in support of a determination or an opinion; a just ground for a conclusion or an action; that which is offered or accepted as an explanation; the efficient cause of an occurrence or a phenomenon; a motive for an action or a determination; proof, more or less decisive, for an opinion or a conclusion; principle; efficient cause; final cause; ground of argument.