Cocktail Attire- A small step above semiformal though not as formal as black-tie optional or formal, cocktail attire is a popular dress code choice. It's a balance between elegant and comfortable, and typically is more formal than a day wedding but more casual than a night celebration. Instead of a floor-length dress, women should opt for a tea-length, knee-length, or midi dress. Men are required to wear a suit and tie, regardless of the wedding's setting. Remember to look classy and polished (Brides.com)
Semi-formal or Dressy Casual Part of dressing for a semiformal or dressy casual wedding is taking the time of the wedding into account. Wear darker, more formal colors for an evening wedding; opt for light colors and fabrics for a daytime event. Try a below-the-knee dress or a dressy skirt and top. An elegant pantsuit is also appropriate. Floor-length gowns, however, would be inappropriate. Pair with heels, nice wedges, or formal flats. If the ceremony is being held outdoors and you'll be walking across a lawn, avoid traditional heels that will likely get stuck in the grass. Men should wear a dress shirt and slacks, dark or light depending on the time of day, with the option to wear a tie. Semiformal gives you flexibility on comfort, but be sure not to dress too casual (Brides.com)