What best defines 'rivalry'?

The term 'rivalry' is best defined as an ongoing competition between two or more parties. This competition often involves individuals, groups, or organizations striving to outperform one another, which can occur in various contexts, such as sports, business, or personal relationships. The essence of rivalry lies in the sustained nature of the competition, characterized by a series of interactions that aim to establish superiority or dominance.

The other options do not capture the core meaning of rivalry. Friendly collaboration indicates a cooperative effort rather than competition. A temporary disagreement suggests a brief conflict without the competitive element inherent in rivalry. An effort to assist denotes support or help given to another, which is contrary to the concept of rivalry that involves competition rather than collaboration. Thus, the choice that reflects the nature of rivalry most accurately is the one that describes it as an ongoing competition.