What is the term for a collective decision to stop buying a certain good or service?

The correct answer is "boycott" because it specifically refers to a collective action taken by individuals or groups to stop purchasing or using a particular product or service as a form of protest against a company or its practices. The intention behind a boycott is often to apply economic pressure to bring about change, whether that be related to ethical issues, social justice, or corporate behavior.

This collective decision highlights the power of consumer choice and can often lead to significant impact if a large enough group participates. It is a strategic method used to express dissatisfaction and compel businesses to modify their behavior or policies.

The other terms provided have distinct meanings: a "strike" typically refers to workers collectively stopping work to demand better conditions; a "protest" is a broader demonstration expressing dissent about various issues; and to "unionize" means to form or join a labor union, which is an organized group of workers aimed at promoting their rights and interests. Each of these concepts contributes to labor and social movements, but they do not involve the specific act of ceasing to buy a product or service as a unified group, which is the essence of a boycott.