definition of
reason

[1] #1 reason n. [ground] a rational motive for a belief or action; "the reason that war was declared"; "the grounds for their declaration". wn

[2] #2 reason n. an explanation of the cause of some phenomenon; "the reason a steady state was never reached was that the back pressure built up too slowly". wn

[3] #3 reason v. [reason out, conclude] decide by reasoning; draw or come to a conclusion; "We reasoned that it was cheaper to rent than to buy a house". wn

[4] #4 reason n. [understanding, intellect] the capacity for rational thought or inference or discrimination; "we are told that man is endowed with reason and capable of distinguishing good from evil". wn

[5] #5 reason v. [argue] present reasons and arguments. wn