Reason is a noun meaning the cause, explanation, or justification for an action or event.
It can also refer to the power of the mind to think, understand, and form judgments logically.
The term "reason" also refers to:
1. A motive or purpose (e.g. "What's the reason for your visit?")
2. Good sense or judgment (e.g. "She lost all reason")
3. In philosophy, the capacity for rational thought