[rea.son] n [ME resoun, fr. OF raison, fr. L ration-, ratio reason, computation, fr. reri to calculate, think; prob. akin to Goth rathjo account, explanation] (13c) 1 a: a statement offered in explanation or justification "gave ~s that were quite satisfactory" b: a rational ground or motive "a good ~ to act soon" c: a sufficient ground of explanation or of logical defense; esp: something (as a principle or law) that supports a conclusion or explains a fact "the ~s behind her client's action" d: the thing that makes some fact intelligible: cause "the ~ for earthquakes" "the real ~ why he wanted me to stay --Graham Greene"
2. a (1): the power of comprehending, inferring, or thinking esp. in orderly rational ways: intelligence (2): proper exercise of the mind (3): sanity b: the sum of the intellectual powers 3 archaic: treatment that affords satisfaction -- in reason : rightly, justifiably -- within reason : within reasonable limits -- with reason : with good cause
[2]reason vb rea.soned ; rea.son.ing vi (15c) 1 a obs: to take part in conversation, discussion, or argument b: to talk with another so as to influence his actions or opinions "can't ~ with her"
2: to use the faculty of reason so as to arrive at conclusions ~ vt 1 archaic: to justify or support with reasons
2: to persuade or influence by the use of reason
3: to discover, formulate, or conclude by the use of reason "a carefully ~ed analysis" syn see think -- rea.son.er n