【Discourse】 , 【expatiate】 , 【dilate】 , 【descant】 are comparable when meaning to talk or sometimes write more or less formally and at length upon a subject.
【Discourse】 frequently implies the manner or attitude of the lecturer, the monologist, or the preacher; it may suggest detailed or logical and sometimes profound, witty, or brilliant discussion.
【Expatiate】 implies ranging without restraint or wandering at will over a subject; it connotes more copiousness than 【discourse】 and often carries a hint of long-windedness.
【Dilate】 implies a discoursing that enlarges the possibilities of a subject (as by dwelling on each small detail).
【Descant】 stresses free comment, but it often also connotes delight or pleasure in this free expression of one’s opinions or observations.
