Which of the following best defines an 'epoch'?

The choice that best defines an 'epoch' is that it refers to a distinct period longer than a person's life. An epoch is not merely a short span of time, but rather a significant and often marked period in history characterized by particular events, developments, or changes that have lasting importance. This term is frequently used in various contexts, including geology, history, and literature, to describe crucial phases that shape societal, cultural, or natural developments over extended durations, often encompassing many generations.

In understanding this definition, it becomes clear why other options are less suitable. For instance, defining an epoch as a brief moment in time (the first choice) contradicts the essence of an epoch being a substantial and noteworthy period. Similarly, while an epoch can certainly relate to important events (the third choice), it encompasses much more than just singular events—it captures broader historical trends or significant shifts. Lastly, describing an epoch as a common era in daily life implies a lack of the historical or impactful connotation that is essential to the meaning of the term; it is not merely about regular, everyday experiences.