The term "formal" refers to something that follows regulations, is a dressy or important occasion, or has official sanctioning or permission. A formal event might be a dinner party in a mansion where everyone dresses up and is very polite. Formality Levels The most formal dress code is "white tie." Tuxedos are worn by men and consist of a black jacket with tails, a white bow tie, and an optional white vest. Floor-length evening gowns in dark colors are popular among women. Men should wear a black tuxedo jacket and a black bow tie, with an optional cummerbund or vest.