White tie is the most formal of dress codes and is usually seen only at diplomatic events, upper-crust awards ceremonies or charity balls.
For men, the dress code consists of a tailcoat, waistcoat and white bow tie - medals are optional.
For women, it entails a floor-length ball gown in an unobtrusive colour and hair worn in an updo, like actress Blake Lively (with her husband, actor Ryan Reynolds, at the 2014 Cannes Film Festival). Elbow-length gloves would not be out of place.
Black tie is a dress code most people are much more likely to encounter.
At evening events, it means a tuxedo for men. "Black tie optional" means men may choose to replace the bow tie with a dressy tie and tie bar, while "black tie creative" is more flexible and allows for variations such as jackets with unusual detailing, patterned accessories or coloured shirts instead of white.
Women may wear dressy pantsuits or shorter dresses to a black tie function, but it is safer to go with a long gown, such as the one lawyer Amal Alamuddin Clooney (with her husband, director-actor George Clooney) wore to this year's Venice Film Festival.
For smart casual, it is safer to err on the smart side.
For instance, men may pair jeans or chinos with a button-down shirt - such as the one on actor Jeffrey Xu (seen here with actress Felicia Chin) - or a blazer thrown over a T-shirt. A tie is not required.
Women can step out in tailored silhouettes and statement bags. As for footwear, either flats or heels are acceptable.
COCKTAIL OR LOUNGE
"Cocktail" and "lounge" both indicate a suit for men, preferably with a skinny tie, such as the one on musician Keith Urban (with his wife, actress Nicole Kidman, at this year's Toronto International Film Festival). For women, this means a knee-length dress or a pantsuit, with accessories and heels.
"Beach formal" is becoming more and more common with the rise in popularity of outdoor weddings.
Linen suits in light colours and leather sandals are acceptable for men, while women may choose dresses in flowy fabrics, including printed maxi dresses, such as this one on actress Penelope Cruz (at this year's Venice Film Festival), or a pastel sheath dress.