Definitions of reason:

• noun:   the capacity for rational thought or inference or discrimination

  Example: "We are told that man is endowed with reason and capable of distinguishing good from evil"

• noun:   a fact that logically justifies some premise or conclusion

  Example: "There is reason to believe he is lying"

• noun:   an explanation of the cause of some phenomenon

  Example: "The reason a steady state was never reached was that the back pressure built up too slowly"

• noun:   a rational motive for a belief or action

  Example: "The reason that war was declared"

• noun:   a justification for something existing or happening

  Example: "They had good reason to rejoice"

• noun:   the state of having good sense and sound judgment

  Example: "He had to rely less on reason than on rousing their emotions"

• verb:   think logically

  Example: "The children must learn to reason"

• verb:   decide by reasoning; draw or come to a conclusion

  Example: "We reasoned that it was cheaper to rent than to buy a house"

• verb:   present reasons and arguments
• name:  A surname (rare: 1 in 100000 families; popularity rank in the U.S.: #8996)