Final answer:
Private goods are defined by their excludability and rivalry in consumption.
Step-by-step explanation:
Private goods are defined by two characteristics: excludability and rivalry in consumption.
An excludable good is one that consumers cannot use without paying for it. For example, pizza is excludable because consumers must pay for it before they can eat it.
A rival good is one that can only be consumed by one person at a time. Pizza is also rivalrous because once one person eats a slice, it cannot be consumed by another person at the same time.
Therefore, the correct characteristics that define private goods are excludable and rival.