reason

reason (http://definr.com/reason)

     n 1: a rational motive for a belief or action; "the reason that
          war was declared"; "the grounds for their declaration"
          [syn: ground]
     2: 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"
     3: 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" [syn:
         understanding, intellect]
     4: the state of having good sense and sound judgment; "his
        rationality may have been impaired"; "he had to rely less
        on reason than on rousing their emotions" [syn: rationality,
         reasonableness]
     5: a justification for something existing or happening; "he had
        no cause to complain"; "they had good reason to rejoice"
        [syn: cause, grounds]
     6: a fact that logically justifies some premise or conclusion;
        "there is reason to believe he is lying"
     v 1: decide by reasoning; draw or come to a conclusion; "We
          reasoned that it was cheaper to rent than to buy a
          house" [syn: reason out, conclude]
     2: present reasons and arguments [syn: argue]
     3: think logically; "The children must learn to reason"