For women, semi-formal attire is somewhat flexible. Women can wear a dress, pant suit or dress suit. Preferred fabrics for semi-formal attire for women include silk, velvet, rayon, cashmere, high quality polyester brocades, or velour.While for men, semi-formal attire means wearing a full suit, with vest optional. A tie, either bow or straight, should be worn, and the shirt should be a simple button down.Suit fabric choices are primarily wool gabardine or cashmere.