Rationale (noun)

A set of reasons or a logical basis for a course of action or belief.

Origin:

Late middle english: from latin rationalis, from ratio(n-) "calculation, reason.".

Examples:

1. The manager explained the rationale behind the decision to lay off employees.
2. The scientist presented the rationale for her hypothesis.
3. The teacher shared the rationale for using the new teaching method.
4. The investor explained the rationale for his investment strategy.
5. The politician justified his vote with a detailed rationale.