Western dress code in the context of "Semi-formal attire"

Formal trousers, also known as formal striped trousers or colloquially spongebag trousers, are grey striped or patterned formal trousers for day attire in traditional Western dress code, primarily associated with formal morning dress or secondly its semi-formal equivalent black lounge suit. Traditionally made from heavy wool ranging from worsted, melton to partial twill weave, the pattern is most often of a muted design in stripes of black, silver, white and charcoal grey in various combinations (not to be confused with pinstripe or chalkstripe, which are formed of single thin lines spaced equally apart). In addition, formal trousers may also come in check patterns, such as houndstooth check, or plaids, although these variants are widely considered as not the most formal.

Typically, formal trousers are intended to be worn with braces with a fishtail back covered by a waistcoat, and have pleats for correct ironing result and comfort. Likewise, for traditional reasons of formality, they do not have turn-ups, since these are considered less formal.

Formal wear or full dress is the Western dress code category applicable for the most formal occasions, such as weddings, christenings, confirmations, funerals, Easter and Christmas traditions, in addition to certain state dinners, audiences, balls, and horse racing events. When formal dress is required, generally permitted alternatives include the most formal versions of ceremonial dresses (including court dresses, diplomatic uniforms and academic dresses), full dress uniforms, religious clothing, national costumes, and most rarely frock coats (which preceded morning coat as default formal day wear 1820s-1920s). In addition, formal wear is often properly worn when displaying official full size orders and medals.

The protocol specifying men's traditional formal wear has remained virtually unchanged since the early 20th century. Despite decline following the counterculture of the 1960s, it remains observed in formal settings influenced by Western culture: notably around Europe, the Americas, South Africa, Australia, as well as Japan. For women, although fundamental customs for formal ball gowns (and wedding gowns) likewise apply, changes in fashion have been more dynamic. Traditional formal headgear for men is the top hat, and for women picture hats etc. of a range of interpretations. Shoes for men are dress shoes, dress boots or pumps, and for women heeled dress pumps. In western countries, a "formal" or white tie dress code typically means tailcoats for men and evening dresses for women. The most formal dress for women is a full-length ball or evening gown with evening gloves. Some white tie functions also request that the women wear long gloves past the elbow.

Morning dress, also known as formal day dress, is the formal Western dress code for day attire, consisting chiefly of a morning coat, waistcoat, and formal trousers for men, and an appropriate gown for women. Men may also wear a popular variant, where all parts (morning coat or waistcoat, and trousers) are the same colour and material, often grey, and usually called "morning suit" or "morning grey" to distinguish it; considered properly appropriate only to festive functions, such as summer weddings and horse races, which consequently makes it slightly less formal. The correct hat would be a formal top hat, or if on less spacious audience settings, optionally a collapsible equivalent opera hat.

Debrett's states that morning dress should not be specified as the dress code for events starting after 6 p.m. If a formal event will commence at or after 6 p.m., white tie should be specified instead. The semi-formal daytime counterpart of this code is the black lounge suit.

Casual wear (or casual attire or clothing) is a Western dress code that is relaxed, occasional, spontaneous and suited for everyday use. Casual wear became popular in the Western world following the counterculture of the 1960s. When emphasising casual wear's comfort, it may be referred to as leisurewear or loungewear.

While casual is "informal" in the sense of "not formal", informal wear traditionally refers to a Western dress code associated with suits—a step below semi-formal wear—thus being more formal than casual attire.

Black tie is a semi-formal Western dress code for evening events, originating in British and North American conventions for attire in the 19th century. In British English, the dress code is often referred to synecdochically by its principal element for men, the dinner suit or dinner jacket. In American English, the equivalent term tuxedo (or tux) is common. The dinner suit is a black, midnight blue or white two- or three-piece suit, distinguished by satin or grosgrain jacket lapels and similar stripes along the outseam of the trousers. It is worn with a white dress shirt with standing or turndown collar and link cuffs, a black bow tie, sometimes an evening waistcoat or a cummerbund, and black patent leather dress shoes or court pumps. Accessories may include a semi-formal homburg, bowler, or boater hat. In Britain, some individuals may rebel from the formal dress code by wearing coloured socks or a bow tie that is not black, such as red. For women, an evening gown or other fashionable evening attire may be worn.

The first dinner jacket is traditionally traced to 1865 on the then Prince of Wales, later King Edward VII (1841–1910). The late 19th century saw gradual introduction of the lounge jacket without tails as a less formal and more comfortable leisure alternative to the frock coat. Thus in many non-English languages, a dinner jacket is still known as the false friend "smoking". In American English, its synonym "tuxedo" was derived from the village of Tuxedo Park in New York State, where it was introduced in 1886 following the example of Europeans. Following the counterculture of the 1960s, black tie has increasingly replaced white tie for more formal settings in the United States, along with cultures influenced by American culture.