A reason is a consideration which justifies or explains. Reasons are what people appeal to when making arguments about what people should do or believe. (Those are reasons in the normative sense.) For example, the fact that a doctor's patient is grimacing is a reason to believe the patient is in pain. The fact that the patient is in pain is a reason for the doctor to do things to alleviate the pain. In another sense of the term, reasons are explanations of why things happened. (These are reasons in the explanatory sense.) For example, the reason the patient is in pain is that her nerves are sending signals from her tissues to her brain. A reason, in many cases, is brought up by the question "why?", and answered following the word "because." Additionally, words and phrases like: since, due to, as, considering (that), a result (of), and in order to, for example, all serve as explanatory locutions that precede the reason to which they refer.