(), also called (), and sometimes referred as "Swallow-tailed Hems and Flying Ribbons clothing" or "swallow tail" clothing for short in English, is a form of set of attire in which was worn by Chinese women. The can be traced back to the pre-Han period and appears to have originated the () of the Zhou dynasty; it then became popular during the Han, Cao Wei, Jin and Northern and Southern dynasties. It was a common form of aristocratic costumes in the Han and Wei dynasties and was also a style of formal attire for elite women. The can be further divided into two categories of clothing style based on its cut and construction: the , and the (or ).
The falls in the category of (long robe); however, some Chinese scholars also classify it as being a type of . On the other hand, the follows (or ) system consisting of a , an upper garment, and a , a long skirt.
The was multi-layered. It was decorated with an apron-like decorative cloth at the waist, with triangular-strips at the bottom, and with pieces of ribbons worn underneath the apron, which would hung down from the waist. The popularity of ribbons later fell and the decorative hems were eventually enlarged.
This form of attire also spread to Goguryeo, where it is depicted in the tomb murals found in the Anak Tomb No.3.
The Chinese character in the term refers to the shape of its hanging part, which is broad at the top but becomes narrow at the bottom, making it look like a , an ancient measuring tool for Chinese medicine.
The term was recorded prior to the Han dynasty in the Ode to Goddess written by Song Yu, a Chinese poet from the late Warring States period. The , which is a form of in the broad sense, appears to have originated from one of the Queen's , a form of ceremonial clothing dating from the Zhou dynasty. According to some Chinese scholars, the attire called in the Han dynasty was in the style of the . However, in the Han and Wei period, the was one of the common aristocratic costumes.
The Han dynasty type of was a . The garment's silk decorations were cut into arch shapes; these originated from the recorded in the Rites of Zhou. The 's popularity started to fade in the late Eastern Han dynasty. A which follows the system also appeared in the Han dynasty, where it was called or .
On the whole, the costumes of the Wei and Jin period still followed the patterns of Qin and Han dynasties. However, the clothing of women in this period was generally large and loose, reflecting a focus on beauty and extravagant expense in buying or weaving cloth. This carefree lifestyle reflected in the apparel can be explained by the historical circumstances which impacted the mood of the people. The Northern and Southern dynasties was a period of volatility, when the northern non-Han peoples collectively known as the Five Barbarians invaded Central Plain, triggering the wars of the Sixteen Kingdoms and Six Dynasties period. As the Han hold on the region collapsed, so did the once unchallenged power of Confucianism. In the meantime, the philosophy of Laozi and Zhuangzi became popular, Buddhist scriptures were translated, Taoism was developed, and Humanitarian ideology emerged among the aristocrats. However, these all posed a threat to conservative and imperial power, which tried to crush them by force. These policies forced these scholars to seek comfort and relief in life. They were interested in various kinds of philosophy and sought to reconcile disparate philosophies through "mysterious learning". They preferred a life of truth and freedom. They dressed themselves in free and casual elegance.
The (or ), which was worn in the Wei, Jin, Northern, and Southern dynasties, was quite different from the style worn in the Han dynasty. It had evolved from the one-piece long robe, either from the or the worn in the Han dynasty, and had wide sleeves.
The are depicted with in the paintings of Gu Kaizhi. The eventually became more popular than the during this period.
The also evolved in terms of shape in the Northern and Southern dynasties when the long ribbons were no longer seen and the swallow-tailed corner became bigger; as a result the flying ribbons and the swallow-tailed corners were combined into one. These changes can be found in the paintings Wise and Benevolent Women and Nymph of the Luo River by Gu Kaizhi, as well as the lacquered paintings unearthed from the Sima Jinlong tomb in Datong and the Goguryeo tomb murals from the Anak Tomb No. 3.
Typically the was decorated with and . The Shao refers to pieces of silk cloth sewn onto the lower hem of the dress, which were wide at the top and narrow at the bottom, so that triangles were formed overlapping each other. "Xian" refers to some relatively long, silk ribbons which extended from the short-cut skirt. While the wearer was walking, these lengthy ribbons made the sharp corners and the lower hem wave like a flying swallow, hence the Chinese phrase "beautiful ribbons and flying swallowtail" ().
There are also two types of . The which follows the 'one-piece system' is called while the other form of , (or ), follows the 'separate system', consisting of which is a set of attire composed of a , an upper garment, and a as a long skirt. The change in the shape and structure of the reflects the historical trend of the fading popularity of in the late Eastern Han and the increase popularity of the (or ) which eventually became the mainstream style in the Wei, Jin, Southern and Northern dynasties.
In the , the upper garment was opened at the front and was tied at the waist. The sleeves were broad and fringed at the cuffs with decorative borders of a different colour. The skirt had spaced coloured stripes and was tied with a white silk band at the waist. There was also an apron between the upper garment and skirt for the purpose of fastening the waist. Apart from wearing a multi-coloured skirt, women also wore other kinds such as the crimson gauze-covered skirt, the red-blue striped gauze double skirt, and the barrel-shaped red gauze skirt. Many of these styles are mentioned in historical records. Wide sleeves and long robes, flying ribbons and floating skirts, elegant and majestic hair ornaments, all these became the fashion style of Wei and Jin female appearance.
During the Northern and Southern dynasties, the underwent further changes in style. The long flying ribbons were no longer seen and the swallow-tailed corners became enlarged; as a result, the flying ribbons and swallow-tailed corners were combined into one.
Depictions of women wearing can also be found in Goguryeo tomb murals, as found in the Anak Tomb No.3. The wife of the tomb owner of Anak Tomb No.3 dresses in Chinese , which may indicate the clothing style worn in the Six dynasties. The tomb belongs to a male refugee called Dong Shou (died in 357 AD) who fled from Liaotong to Goguryeo according to Chinese scholar Yeh Pai, a conclusion which is also accepted in the formal Korean report issued in 1958 although some Korean scholars believe the tomb to belong to King Mi-chon.