What is the meaning of reason?

noun

• A rational motive for a belief or action.
  • usage: "the reason that war was declared"; "the grounds for their declaration"
  • synonyms: ground
• An explanation of the cause of some phenomenon.
  • usage: "the reason a steady state was never reached was that the back pressure built up too slowly"
• The capacity for rational thought or inference or discrimination.
  • usage: "we are told that man is endowed with reason and capable of distinguishing good from evil"
  • synonyms: understanding, intellect
• The state of having good sense and sound judgment.
  • usage: "his rationality may have been impaired"; "he had to rely less on reason than on rousing their emotions"
  • synonyms: rationality, reasonableness
• A justification for something existing or happening.
  • usage: "he had no cause to complain"; "they had good reason to rejoice"
  • synonyms: cause, grounds
• A fact that logically justifies some premise or conclusion.
  • usage: "there is reason to believe he is lying"

verb

• Decide by reasoning; draw or come to a conclusion.
  • usage: "We reasoned that it was cheaper to rent than to buy a house"
  • synonyms: reason out, conclude
• Present reasons and arguments.
  • synonyms: argue
• Think logically.
  • usage: "The children must learn to reason"