Formal trousers in the context of "Morning dress"

Trousers (British English), slacks, or pants in (Northern English, American, Canadian and Australian English) are an item of clothing worn from the waist to anywhere between the knees and the ankles, covering both legs separately (rather than with cloth extending across both legs as in robes, skirts, dresses and kilts).Shorts are similar to trousers, but with legs that come down only as far as the knee, but may be considerably shorter depending on the style of the garment. To distinguish them from shorts, trousers may be called "long trousers" in certain contexts such as school uniform, where tailored shorts may be called "short trousers" in the UK.

The oldest known trousers, dating to the period between the thirteenth and the tenth centuries BC, were found at the Yanghai cemetery in Turpan, Xinjiang (Tocharia), in present-day western China. Made of wool, the trousers had straight legs and wide crotches and were likely made for horseback riding. A pair of trouser-like leggings dating back to 3350 and 3105 BC were found in the Austria–Italy border worn by Ötzi. In most of Europe, trousers have been worn since ancient times and throughout the Medieval period, becoming the most common form of lower-body clothing for adult males in the modern world. Breeches were worn instead of trousers in early modern Europe by some men in higher classes of society. Distinctive formal trousers are traditionally worn with formal and semi-formal day attire. Since the mid-twentieth century, trousers have increasingly been worn by women as well.

A frock coat is a formal men's coat characterised by a knee-length skirt cut all around the base just above the knee, popular during the Victorian and Edwardian periods (1830s–1910s). It is a fitted, long-sleeved coat with a centre vent at the back and some features unusual in post-Victorian dress. These include the reverse collar and lapels, where the outer edge of the lapel is often cut from a separate piece of cloth from the main body and also a high degree of waist suppression around the waistcoat, where the coat's diameter around the waist is less than around the chest. This is achieved by a high horizontal waist seam with side bodies, which are extra panels of fabric above the waist used to pull in the naturally cylindrical drape. As was usual with all coats in the 19th century, shoulder padding was rare or minimal.

In the Age of Revolution around the end of the 18th century, men abandoned the justaucorps with tricorne hats for the directoire style: dress coat with breeches or increasingly pantaloons, and top hats. However, by the 1820s, the frock coat was introduced along with full-length trousers (pants), perhaps inspired by the then casual country leisure wear frock. Early frock coats inherited the higher collars and voluminous lapels of the dress coat style at the time, and were sometimes offered in different, albeit increasingly dark, colours. Within a few years, though, plain black soon became the only established practice, and with a moderate collar. The top hat followed suit.

The black lounge suit (UK), stroller (U.S.), or Stresemann (Continental Europe), is a men's day attire semi-formal intermediate of a formal morning dress and an informal lounge suit; comprising grey striped or checked formal trousers, but distinguished by a conventional-length lounge jacket, single- or double-breasted in black, midnight blue or grey. This makes it largely identical to the formal morning dress from which it is derived, only having exchanged the morning coat with a suit jacket, yet with equivalent options otherwise, such as necktie or bowtie for neckwear, a waistcoat (typically black, grey, or buff), French cuffs dress shirt of optional collar type, and black dress shoes or dress boots. The correct hat would be a semi-formal homburg, bowler, or boater hat. Just as morning dress is considered the formal daytime equivalent of formal evening attire dress coat i e. white tie, so the stroller is considered the semi-formal daytime equivalent of the semi-formal evening attire dinner jacket, i.e. black tie (also called tuxedo). Unlike other dress codes, there is no clear equivalent for women, though typical morning dress and cocktail dress have both been identified as alternatives.

Wearing a black lounge suit the traditional way with formal trousers largely fell out of use following the counterculture of the 1960s, although its practice has still been observed occasionally ever since.