reason

(noun) a rational motive for a belief or action. Synonyms: ground. Examples: "The reason that war was declared." "The grounds for their declaration."

(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) the capacity for rational thought or inference or discrimination. Synonyms: understanding, intellect. Example: "We are told that man is endowed with reason and capable of distinguishing good from evil."

(noun) the state of having good sense and sound judgment. Synonyms: rationality, reasonableness. Examples: "His rationality may have been impaired." "He had to rely less on reason than on rousing their emotions."

(noun) a justification for something existing or happening. Synonyms: cause, grounds. Examples: "He had no cause to complain." "They had good reason to rejoice."

(noun) a fact that logically justifies some premise or conclusion. Example: "There is reason to believe he is lying."

(verb) decide by reasoning; draw or come to a conclusion. Synonyms: reason out, conclude. Example: "We reasoned that it was cheaper to rent than to buy a house."

(verb) present reasons and arguments. Synonyms: argue.

(verb) think logically. Example: "The children must learn to reason."