Corollary is a noun that refers to something that follows naturally.
The Latin word corolla (co ROLL uh) refers to a ‘gratuity’ or ‘bonus’ given to people. You could think of a corollary as a bonus observation.
For example: As a college professor, I often find it helpful to offer a corollary to my statements to drive the point home. Sometimes a bonus thought can make the abstract more concrete.