I don't know why exactly, but the misuse of math terms drives me up the wall, as anyone who's heard me complain about the phrase "one-dimensional characters" can attest. The most recent term to attract my ire is the ol' love triangle, which seldom is ever a true triangle. Most people think of a love triangle as being between three people where one individual has to choose between two others of the opposite gender. There are three people, so that's where the triangle comes in