English definition of “reason”
WHY [C] › the facts about why something happens or why someone does something: I knew Sam was going - that was the reason I went there. Is there any particular reason why he doesn't want to come? He left without giving a reason. That was the reason for telling her.
RIGHT [C, U] › something that makes it right for you to do something: [+ to do sth] There is every reason to believe the project will be finished on time. I think we have reason to be concerned.
ABILITY [U] › the ability to think and make good decisions: By this time he'd lost his powers of reason.
within reason › If something is within reason, it is acceptable and possible: You can have as much as you like, within reason.