Monetary means relating to money. When economists talk about monetary policy, they're discussing how governments and banks manage the amount of money circulating in an economy. When a court orders someone to pay monetary damages, they must pay money rather than serve time or perform some other penalty.

The word helps distinguish money matters from other kinds of value or exchange. A museum might accept monetary donations (cash or checks) as well as donated artwork or artifacts. Your allowance represents a monetary reward for completing chores, while a compliment from your parent is a different kind of reward entirely.

You'll often see monetary in formal contexts: news reports about monetary systems, history books describing monetary reforms, or business discussions about monetary transactions. It's a more precise, technical way of saying “related to money” when you want to sound exact and professional.