Other forms: preachers
A preacher is a Christian religious leader. On Sundays, preachers deliver sermons in churches.
While it's possible to preach, or proclaim publicly, about non-religious topics, you're most likely to find the word preacher describing an evangelist Christian minister or pastor. There are also informal street preachers who preach the gospel to people who walk by. Preacher comes from the Latin word praedicatorem, "public praiser," or "proclaimer."