A sermon is a speech about religious or moral topics, usually given by a religious leader during a worship service. When a minister, rabbi, or imam delivers a sermon, they might explain a passage from their holy book, share wisdom about how to live, or help their congregation think about difficult questions.

Sermons have been central to religious practice for thousands of years. In many churches, the sermon comes after readings from the Bible, and the preacher helps explain what those ancient words mean for people today. A good sermon makes you think, sometimes challenges you, and often tells stories that help illustrate a larger point.

The word can also describe any long, tedious lecture about how you should behave. If your older brother gives you a sermon about cleaning your room, he's lecturing you in that preachy, drawn-out way that makes you want to roll your eyes. When someone sermonizes, they're speaking in this moralizing, lecture-like manner, whether or not they're in a place of worship.