Semi Formal Attire
When discussing dress codes, semi formal attire is one of the least understood and most often misinterpreted dress guidelines.
For men the idea of semi-formal attire is actually quite simple to understand and easy-to-follow. A simple business suit is all that is required to be appropriately dressed for a semi formal event. The suit can be worn with or without a vest or waistcoat, though must always be worn with a necktie and dress shoes.
Really, the only important thing to keep in mind is to not choose too casual of a suit for the semi formal event. Linen and light colored suits are considered to be too casual therefore classic wool, cashmere and various blends are generally preferred. Additionally you do not want to overdress for a semi formal event, thus do not be tempted to wear a tuxedo as this would be considered too formal.