Business Casual:
business casual means dressing professionally, looking relaxed yet neat and pulled together.
* For men: a shirt with a collar (dress or polo shirt) and cotton trousers (or "khakis" in American English).
A blazer or business jacket can optionally be added.
* For women: a tennis shirt and trousers.

Interview Attire:
A two-piece matched suit is always the best and safest choice.

Formal:
A Black Tie invitation calls for formal attire. Men wear tuxedos, women wear cocktail, long dresses or dressy evening separates.

Formal usually means the same as Black Tie, but in some trendier cities like New York or Los Angeles, it could mean a black shirt, no tie with a tux. Women wear cocktail, long dresses or dressy evening separates.

Informal:
A nice shirt with collar and perhaps a tie for the men, and a stylish day dress or similar for the female guests.

Men's Suits (Style, pant length, buttons, ...)

Business:
Always wear neutral, conservative colors whether in a suit or other clothing.

Weddings:
If the invitation doesn't specify the type of attire or it's frustratingly unclear what style of men's suit would be most appropriate (the most likely occurrence), base your decision on the time of day and the season in which the wedding is taking place. The best way to judge what you should be sporting to an evening wedding in the fall or winter is by analyzing the invitation. If a type of attire isn't specified in the invite, judge the extent of the wedding's formality by the actual invite itself. Is it a simple card with basic or casual wording? If so, chances are it's going to be an informal, basic-black-suit sort of thing. Is the invitation written in fancy script with formal language? This would be a clear indication that a tuxedo is probably your best bet."
Source: Wedding Fashion - AskMen

Black tie, formal and semi-formal are defined in the links below.
Informal is more difficult to decode. Unless the wedding is to be very, very casual, 'informal' still means a nice shirt with collar and perhaps a tie for the men, and a stylish day dress or similar for the female guests. Very rarely 'informal' mean shorts, jeans or anything else made of denim.
See also:
Wedding Guests: Wedding Guest Attire Cheat Sheet - TheKnot.com
Decoding The Dress Code - Ask Bronny
8 Dos And Don'ts Of Wedding Guest Attire | YourTango

Chinese:
Red is the prevailing color in Chinese weddings. In Chinese culture, red symbolizes love, happiness and luck according to Cultural China. Red is also thought to bring prosperity.
For Chinese weddings, some colors are unfavorable and should not be used. White should be avoided because it symbolizes death and mourning, according to Chinese Weddings by The Knot. Blue, black and gray are omitted as well because of their association with unhappy matrimony.

Funeral:
Deceased < 80 years old - Dark colors
Deceased ≥ 80 years old - Whie

Books:

Links:
Party Definitions: Black Tie, Formal, Casual, Cocktail Attire and More
Dress Code Guide
Dress code - Wikipedia
Interview appearance and attire | Career Services | Virginia Tech
Facts About Chinese Business Attire | eHow.com
Chinese Wedding Colors | eHow.com
Chinese Wedding Attire Basics - Chinese Wedding Fashion - Chinese Wedding Dresses