Formal wear (more often in the United States) or formal dress (in the United Kingdom) is a general fashion term used to describe clothing suitable for formal events, including weddings, debutante cotillions, etc. Western formal wear has had a pervasive influence on styles in many countries. It is almost always the standard used in countries where there is no formal version of the national costume. Foreign dignitaries and honoured guests in Western countries often adopt Western evening dress on formal and state occasions, although it is not uncommon for distinguished persons to wear the formal versions of their national dress if such exists; the sari and the dashiki are easily-recognizable examples.
Unlike most of the fashion world, the styles of formal attire take their names from men's wear rather than female attire. Traditional 'rules' govern men's formal dress; these are strictly observed at socially conservative events such as royal weddings, and serve as starting points for the creative formal wear seen at high school proms, formal dances and entertainment industry awards shows.

Civilian formal wear can be categorized by dress codes. In the early decades of the twentieth century, the codes in England, Europe and North America were universally accepted as:

· Formal evening wear, also known as Full Dress or white tie
· Semiformal evening wear, or black tie
· Formal daytime dress, or morning dress
· Semiformal daytime dress (stroller)
· Informal dress (lounge suits)

The continual relaxing of formal standards since World War II have led to a blurring of what constitutes “formal” and “semi formal”. While pedigreed etiquette and menswear experts tend to still use the traditional terms — particularly when describing dress codes for weddings — many other consultants use more contemporary labels and definitions. It is now common to see white tie described as “very formal” or even “ultra formal” and black tie labeled as “formal”. Even the lounge suit, traditionally regarded as informal wear is sometimes worn as a type of pseudo-formal wear. Additionally, modern advisors allow for black tie at the most formal of events and for black tie alternatives at any other type of formal occasion. Subsequently it has become common to use the terms “white tie” and “black tie” to differentiate these specific dress codes from the more ambiguous and contextual “formal” or “semiformal” labels.
The older terminology used in the nineteenth century and even early in the twentieth century was 'full dress' as opposed to 'half dress' and 'undress'.

In the UK, the two evening categories are known as “evening dress” and the day categories are known as “morning dress” because “day wear” is considered informal dress. Daytime formal dress has become extremely rare in the United States where morning dress has been replaced by strollers or even lounge suits. However, in the United Kingdom, Europe, Australasia and even in Japan morning dress is still worn.

Styles of Formal Wear :

The degrees of formal wear and its component elements are described in the individual fashion article below:
Men's Styles

Teenage boys attending a black tie high school prom.

Evening styles:

· Court dress — for wear at Royal court
· White tie (Tailcoat)
· Black tie (dinner jacket in British English, tuxedo in American English)