Incentive
Part of speech: noun
Definition: Something that motivates, rouses, or encourages. A bonus or reward, often monetary.
Example sentence: Doubt is the incentive to truth and inquiry leads the way.
Bonus
Part of speech: noun
Definition: Something extra that is goodAn extra sum given as a premium, e.g. to an employee
Part of speech: verb
Definition: To pay a bonus, premium
Example sentence: For me, success isn't even about money. It's about getting to do what you love and supporting yourself. Everything that comes after that is bonus, unless your only goal is to be rich. If that's your goal, you're going to find out that once you have a little bit, you want a lot. Then once you have a lot, you want a lot more.