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"
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"
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"
a fact that logically justifies some premise or conclusion
"there is reason to believe he is lying"
A cause:
"The sudden rain was the reason we canceled our picnic plans."
That which causes something: an efficient cause, a proximate cause.
"The sudden drop in temperature was the reason the lake froze over within hours."
In plain English: Reason is the ability to use your brain to think clearly and make good decisions based on facts rather than just feelings.
"The reason he was late was that his car broke down."
decide by reasoning; draw or come to a conclusion
"We reasoned that it was cheaper to rent than to buy a house"
To deduce or come to a conclusion by being rational
"After carefully examining all the evidence, she was able to reason that the missing keys had been taken by someone inside the house rather than stolen from outside."
In plain English: To reason is to use your brain to think logically and figure out how things work.
"He asked me to reason with my brother about his anger."
Usage: Use this verb when you are forming a logical judgment based on facts, as in "I reasoned that the door was locked." It differs from simply stating an opinion because it implies a process of thinking through evidence.
A surname.
"The Reason family has lived in that valley for over two hundred years."
The word "reason" entered English from Anglo-Norman and Old French, where it originally meant a calculation or reckoning. It ultimately traces back to a Proto-Indo-European root meaning "to think," replacing the native Old English word rǣden.