What defines a “public good”?

A public good is characterized by its availability to all individuals without direct exclusion and is typically funded or provided by the government. This definition is significant because public goods possess two key features: they are non-excludable and non-rivalrous. Non-excludable means that once the good is provided, no one can be effectively excluded from using it, and non-rivalrous means that one person’s use of the good does not diminish another person's ability to use it. Examples of public goods include national defense, public parks, and clean air.

Understanding the nature of public goods is essential in economics and public policy, as it highlights the role of the government in providing services that benefit society as a whole, especially when private markets might fail to provide these necessities efficiently or at all.