Use “disquisition,” meaning “a formal inquiry or discussion,” when you want to point out someone who gave a long-winded reply when a one-word answer would have sufficed. When used as a synonym for “speech,” it can be an upgrade from “rant” or “lecture.” The other usage, that of an inquiry, is more directly related to its Latin root, “quaerere,” meaning “to seek.” This is the same root that gave us the English words “query” and “question.”