Which term refers to an ongoing competition between individuals or groups?

The term that describes an ongoing competition between individuals or groups is "rivalry." This word specifically implies a consistent and often intense competition where adversaries strive to outdo one another, typically in pursuit of the same goals or rewards. Rivalries often have historical context, emotional stakes, or personal vendettas attached to them, distinguishing them from mere competition.

In contrast, the other options carry different meanings. An alliance refers to a relationship formed for mutual benefit, typically between countries or organizations; it does not suggest competition. Conflict denotes a struggle or disagreement but does not inherently imply an ongoing competitive nature; it can be one-time or episodic. Collaboration involves working together towards a common goal, which again stands at odds with the concept of competition. Thus, "rivalry" is the most appropriate term to describe the situation of ongoing competition.