When someone receives direct benefit from someone else's purchase of something, they are \( a(n) \) victim of government failure. thief. externality. free rider.

The correct term for someone who receives a direct benefit from someone else's purchase without contributing to the cost is a **free rider**. Here's a brief explanation of the options: - **Victim of government failure**: This refers to situations where government intervention does not lead to the desired outcomes, often leading to inefficiencies. - **Thief**: This implies illegal taking of someone else's property, which does not fit the context of receiving benefits from another's purchase. - **Externality**: This refers to a situation where a third party is affected by the economic activities of others, but it does not specifically denote the benefit received without payment. - **Free rider**: This is the correct term, as it describes someone who benefits from resources, goods, or services without paying for them, relying on others to shoulder the costs. Thus, the answer is \( a(n) \) **free rider**.