Sermons are usually, but not always, delivered in a house of worship, most of which have a pulpit or ambo, an elevated architectural feature. A sermon is also known as a homily within the Catholic Church. The word "sermon" comes from a Middle English word which was derived from an Old French term, which in turn came from the Latin word sermō; ("discourse"). The word can mean "conversation", which could mean that early sermons were delivered in the form of question and answer, and that only later did it come to mean a monologue. In contrast to this, is the examples from the Bible, where sermons are speeches without interlocution: Moses's sermon in Deuteronomy 1-33; Jesus's sermon on the mount in Matthew 5-7; Peter's sermon after Pentecost in Acts 2.

In modern language, the word "sermon" can also be used pejoratively in secular terms to describe a lengthy or tedious speech delivered with great passion, by any person, to an uninterested audience. A sermonette is a short sermon (usually associated with television broadcasting, as stations would present a sermonette before signing off for the night).