Final answer:
A good that can be consumed by one individual without affecting the amount available to others is known as a public good, which is non-rival and often non-excludable like national defense.
Step-by-step explanation:
If the consumption of a good by one individual does not change the amount of the good available to others, the good is considered to be a public good. A key characteristic of a public good is that it is non-rival. This means that when one person utilizes the public good, the availability of the good for someone else does not diminish; both can benefit from it simultaneously. An example of a public good is national defense: one person's safety provided by national defense does not reduce the safety for another person. Public goods are also typically non-excludable, meaning that once they are provided, no one can be prevented from enjoying them, leading to a situation where individuals can utilize the good or service, usually without direct charge.