When something is meaningless or insignificant because it is so little, it's negligible. The amount of interest you'll get on your savings is negligible, so you might as well spend your money.
If you work really hard on something, but the praise you get for it is negligible, you won't try so hard next time. Besides meaning very small, negligible can mean unimportant or not worth paying attention to. If you get into a fender-bender, you've gotten into a car accident with negligible damage. School concert programs always offer a word of thanks to the principal and other members of the administration whose role in the concert seems to be negligible.