“Cocktail attire was once the crown jewel of mid-20th-century soirées, ... On the most formal end of the cocktail scale, you’d be expected to show up in a dark suit (think: navy, ...

"Formal suits and ties are acceptable." 08 of 10. Black-Tie . Edward Berthelot / Getty Images. What it means: In a word: Fancy. You'll want to pull out all the stops for this one—heels, gowns ...