Define the term public good and give me two examples of public goods.

A public good is a good or service which is both non-rival and non-excludable. Non rival means that one person consuming the good does not stop somebody else from consuming it. For example, cake is rival, as if I eat a particular cake, nobody else can eat that same cake. Non-excludability refers to an inability to bar people from consuming the good; nobody can stop me from consuming street lamps when I walk down the street. Two examples of public goods are defence and street lighting.