A digression is when someone wanders away from their main topic while speaking or writing. If your teacher is explaining how volcanoes form and suddenly starts talking about the time she visited Hawaii, then returns to volcanoes, that's a digression.

Digressions can be frustrating when you're trying to follow an explanation or story. Imagine reading an adventure novel where the author keeps interrupting the action to describe what characters ate for breakfast. Those side trips pull you away from what you really want to know.

But sometimes digressions add useful context or entertaining details. A history book might digress to explain an interesting background fact, or a speaker might share a relevant personal story before returning to the main point. The key is whether the side trip helps or just wastes time.

Writers sometimes apologize for their digressions: “But I digress...” means “I'm getting off track, let me return to my point.” Someone who frequently goes off topic might be called digressive. Scientists and mathematicians value staying focused, but storytellers and essayists sometimes use planned digressions to enrich their work. The difference between a good digression and a bad one often depends on whether it adds something worthwhile or just confuses your audience.