These nouns apply to public speaking, denoting talks delivered before an audience. Speech is the most general and least formal word. A speech may be either extemporaneous or prepared; it may express feelings, ideas or opinions, impart information, related experiences, set forth a programme or outline a position: a campaign speech ; a prepared speech ; an impromptu speech ; an after-dinner speech . An address is a carefully prepared, formal speech; as one delivered by a distinguished speaker or made on a ceremonial occasion: an inaugural address ; a graduation address . Also whereas speech emphasizes the act of talking, address stresses the fact that an audience is in attendance: a malcontent making speeches on street corners; the chairman’s annual address to the shareholders.

An oration is an eloquent address meant to stir the emotions of a group or mass of people. It treats some important subject in a dignified style and manner, according to the rules of oratory, and is usually delivered on a special occasion, as at a celebration or a funeral: Mark Antony’s oration over the body of Caesar; Lincoln’s Gettysburg Address was an oration . Since true orators are rare, the term oration may be applied also to a pompous speech designed for showy, oratorical effect: a small-town Anzac Day oration . A harangue is a long, loud, vehement speech, appealing to passions or prejudices. It may be an extemporaneous tirade and is often intended to inflame those to whom it is addressed and to spur them to action of some sort: the harangues of a demagogue. In a looser sense, harangue may apply to any long, bombastic speech, typically a tiresome one: endless harangues .

Where oration and harangue emphasize the character of an address , the remaining nouns stress content and purpose. A discourse is a fairly long, carefully prepared, well-organized speech on a definite subject: a discourse on Virgil; a collection of religious discourse. A lecture is the kind of speech given by a university teacher to a class. It is a discourse on a given topic, designed to inform and instruct a group of students or some similar audience: a lecture course as distinguished from a series of seminars; adult-education lectures on modern art. Lecture derives from a Latin verb meaning to read. The most effective lectures are not read, but giving a lecture does imply extensive previous preparation, including the writing down of what is to be said.

Both sermon (the general word) and homily (the more erudite term) may mean an instructive religious discourse delivered by a clergyman to a congregation. Originally, a homily was a discourse or lecture explaining a Biblical text, while a sermon was an address from the pulpit dealing with dogma or ethics. Now the opposite distinction is sometimes made ?that a sermon takes its theme from Scripture while a homily gives practical ethical guidance. In the Middle Ages, homilies written by eloquent and learned early churchmen were often read in churches, being used as approved sermons . Hence the branch of theological study that treats of the art of planing, writing and delivering sermons is called "homiletics."

In informal use, lecture , sermon and harangue may all imply didactic moral instruction, referring to formal reproofs, stern rebukes, lengthy reprimands or earnest exhortations to duty.

• He gave the boy a lecture on his lateness; She was subjected to a harangue on her supposed ingratitude; "All right, I’ll do it," he said; "you don’t have to preach me a sermon about it.

Spiel , originally an Americanism, refer to a special kind of talk in which the speaker might be quite garrulous, aggressive or dogmatic. Essentially, a spiel presents a "line" or type of sales talk in a rather set, identifying pattern: His spiel was too long-winded and exaggerated to be convincing; What a spiel he has! It is sometimes used in a slangy way for talk in general.