Semi-formal attire is elegant but still casual, making it appropriate for weddings, cocktail parties and upscale dining. It differs from formal attire in that men are not required to wear tuxedos, and women are not required to wear long dresses.
A man should avoid wearing a tuxedo in semi-formal settings in favor of a dark-colored suit and tie with dressy shoes and other accents. Women can choose to wear classic, black dresses or knee-length cocktail dresses instead of long evening gowns. However, if the event is being held outdoors or during the day, it is appropriate for men to wear light-colored suits and ties, and women are permitted to wear sundresses or dressy blouses paired with a skirt.