Title: Dai (Spring and Autumn period)
Content:  Not to be confused with the various other states of Dai in Chinese history.  Dai was a state which existed in northern Hebei during the Spring and Autumn Period of Chinese history. Its eponymous capital was located north of the Zhou Kingdom in what is now Yu County. It was apparently established by the people known to the ancient Chinese as the Baidi or "White Barbarians". They traded livestock and other goods between Central Asia and the Zhou states prior to their conquest by the Zhao clan of Jin.
Title: Dai (Sixteen Kingdoms)
Content:  Not to be confused with the Dai Commanderies in Northern Yan and Northern Wei during the same period or with other states named Dai in Chinese history. Dai, also rendered as Tai, was a dynastic state ruled by the Xianbei clan of Tuoba, during the era of Sixteen Kingdoms in China. It existed from AD 310 to 376, with its capital at Shengle (盛樂) (near modern Horinger County of Hohhot, Inner Mongolia). The name "Dai" originated when Tuoba Yilu was appointed the Duke of Dai (代公) by the Western Jin dynasty in 310 AD, as a reward for helping Liu Kun (劉琨), the Governor of Bingzhou (并州), fight against the Xiongnu-led Han Zhao dynasty. The fief was later promoted from a duchy to a principality. Dai was conquered in 376 by the Former Qin dynasty, and its descendants later established the Northern Wei dynasty in the 4th century.
Title: Dai (Spring and Autumn period)
Content:  Dai continued to be used as a name for the surrounding region, eventually becoming the namesake for Dai Prefecture and Dai County in Shanxi. The former site of ancient Dai in Yu County, Hebei, is now preserved as "Dai King City" (, Dàiwángchéng), honoring the memory of the Zhao prince Jia, who created a rump state at Dai to oppose King Zheng of Qin in the decade before his successful unification of China as the Qin Empire.
Title: Dai language (Austronesian)
Content:  Dai is a minor Austronesian language spoken on Dai Island in South Maluku, Indonesia.
Title: Dai (Warring States period)
Content:   Not to be confused with the various other states of Dai in Chinese history. Dai was a short-lived state from 228 BC to 222 BC during the Warring States period of Chinese history. Prince Zhao Jia, older brother of King Youmiu of Zhao, fled with the remnant forces to Dai Commandery after the conquest of Zhao and was proclaimed the new king of Zhao. His rump state was conquered in the year 222 BC by Qin during its campaigns against Yan. The ruins of his capital are preserved in present-day Yu County, Hebei, as "Dai King City" (代王城).
Title: Dai Prefecture
Content:  in which Daizhou is located, had not been part of it. The commandery in turn had been named after the former capital of the Baidi Kingdom of Dai, whose name represented a transcription of the native name using the Chinese character, which is pronounced dài in present-day Mandarin but had probably sounded like /*lˤək-s/ in Old Chinese. That city had been in Hebei's Yu County, but it was used for a series of petty states and appanages during the Warring States, Eighteen Kingdoms, and Han which spread the name into Shanxi's Yanmen and Yunzhong Commanderies. This confusion sometimes caused some medieval writers to erroneously conflate locations in Dai Prefecture (like Mount Wutai) with places from the ancient stories concerning the Zhao conquest of the first Dai Kingdom.
Title: Dai Prefecture
Content:  Dai Prefecture was created by renaming and reorganizing the earlier Si Prefecture in Yanmen Commandery. This occurred in AD585 under the Wen Emperor of Sui. Its seat was at present-day Daixian, which was known as Guangwu until 598 and then as Yanmen when its surrounding county was renamed due to the Chinese naming taboo. It was abolished and merged with Yanmen Commandery. Dai Prefecture was reëstablished by the Tang in 618, abolished and merged with Yanmen Commandery again in 742, and reëstablished a second time a few years later in 758. Under the Tang, it formed part of Hedong Circuit. During this period, the seat at Daizhou administered a prefecture covering what are now the counties of Dai, Wutai, Fanshi, and Yuanping. Under the Hongwu Emperor of the Ming, it was demoted to a county for six years beginning in 1369. Under the Qing, Dai was removed from the authority of Taiyuan Prefecture and made a directly-administered prefecture in 1724 or 1728. Following the Xinhai Revolution, it was converted into various counties in the Republic of China.
Title: Yu County, Hebei
Content:   The area was home to the capital of the state of Dai during the Spring and Autumn Period of the Zhou Dynasty. Under the Qin Dynasty, present-day Yu County was organized as Dai County, with its seat Daixian located northeast of present-day Yuzhou. Daixian also served as the capital of Dai Commandery, overseeing 11 or 13 counties in what is now northwestern Hebei and northeastern Shanxi. Under the Eastern Han, the commandery seat was moved west to Gaoliu (near present-day Yanggao in Shanxi). It returned to Daixian near present-day Yuzhou under the kingdom of Wei during the Three Kingdoms Period before the commandery was abolished in 388. (A separate Dai Commandery was established by the Northern Wei in the 520s, with its seat at Pingcheng, just northeast of present-day Datong in Shanxi.) The city was a former garrison town during the Ming dynasty, serving as part of the defense system protecting the capital Beijing from Mongol invasion.
Title: Dai people
Content:  In 109 BCE, the Han Dynasty established the Yizhou prefecture in the southwest of Yi (modern day parts of Yunnan, Sichuan, and Guizhou). In the twelfth century, the Dai (called Dai-Lue or Tai-Lue at this period) established the Jinghong Golden Hall Kingdom in Sipsong Panna (modern Xishuangbanna). Jinghong was the capital of this kingdom. The population of the kingdom was over one million and recognized the Chinese as their sovereign according to local records. The king had political and economic power and controlled most of the land and local water system.
Title: Dai County
Content:  Since 2001, Dai County has been divided into six towns and five townships: These 11 township-level divisions are in turn divided into eight residential communities and 377 villages (2015). The county seat is at Shangguan, with the main offices located on its East Main Street ( t, s , Dōng Dàjiē).

Question: What is Dai the capital of?
Answer: Northern Wei.