The main difference between so-called expository and so-called topical sermons is the proportion and sequencing of these elements. A thirty-minute sermon at a Sunday church service to average, biblically literate church members might have a five-minute introduction, a twenty-minute Bible section, and a five-minute application. But a fifteen-minute Friday lunchtime talk at a cafeteria to office workers might have a four-minute introduction, a one-minute Bible section, and a ten-minute application.