There was a major difference between the pre- and post-Qin dynasties in terms of their size and scale, their political structure, and their core ideas of how the "dynasty" related to Chinese civilization as a whole.

​

For the Shang and Zhou, "China" was not a single country but a cultural sphere made up of many small states paying homage to a central King (Chinese wang 王). Based on evidence from deciphered Oracle Bones, the late Shang only effectively ruled an area corresponding about to modern Henan province, while archaeological finds of Shang-style burials, buildings and religious implements cover a much broader area running from modern Beijing to the north bank of the Yangzi- these were their various independent allies and vassals. The Zhou state was originally one such allied people, and first ruled over the Wei River Valley in modern Shaanxi in the Western Zhou period then moved their administration to modern Luoyang in Henan during the later Eastern Zhou period. The Zhou tied their allies and vassals to themselves more closely than the Shang did, implementing something more like a feudal hierarchy of various junior and senior lineages, but they still only directly administered a relatively small core territory and were neither willing nor able to micromanage the vassal states. These vassals had their own laws and political institutions, their own coinage, even their own variants of the Chinese script. As the outer vassals, including Qin, Jin, Qi and Chu, continued to expand in size and power, the Zhou eventually lost all real temporal power and their subjects cast aside their former feudal ranks and proclaimed themselves Kings in their own right- these kingdoms were all eventually subjugated by the kingdom of Qin in 221 BC, ending the Zhou dynasty.

​

The then-King of Qin, Ying Zheng, created a new title for himself, superior to the title "King" 王 which had been claimed by the Shang, Zhou and Warring States rulers. This title, huangdi 皇帝 or "Emperor," would be used by all subsequent Chinese dynasts, even ones of foreign origin like the Mongol Yuan and Manchu Qing. He also abolished the regional institutions of the former states, applying Qin's three-tier territorial administration, unified law code, and standardized scripts, weights and measures, and system of taxation and labor service across the whole of Chinese civilization. Although the Qin dynasty only reigned over a unified China for 14 years, their system of rule was carried over almost entirely by the Han, who reigned for four centuries and firmly established the principle of a unitary Chinese state with a single ruler and standardized imperial administration. From Han times onward, it was understood that there could only be one Emperor who by rights should rule all of China, where before the Qin it was understood that China was a multi-state civilization where a King had the highest social and religious status but allowed local and regional elites to govern themselves. This is why the Zhou and Shang (and Xia, if you're in the camp that believes they existed) are considered pre-Imperial while the Qin, Han and others are regarded as Imperial.