What is the definition of semi-formal attire?

For women, semi-formal attire usually consists of a cocktail dress or a skirt and blouse, though trousers are also acceptable. Semi-formal attire for men generally consists of a dark suit or odd trousers and a blazer. Men are also usually expected to wear a tie.

Semi-formal attire may also be called cocktail attire. It is not as formal as black tie attire, but more formal than business casual or dressy casual. It is also distinct from business attire, in that it may be somewhat less conservative. Some events where cocktail attire may be expected include weddings, parties and special events.