天体、天气的运行变化及其规则。出自《周易》。日月星辰的运行、四季昼夜的交替、寒暑风雨的变化，都呈现出某种恒常的法则，这即是“天文”。古人认为，人伦生活与天地万物遵循着相通的法则。因此，人们可以通过对“天文”的观察与效法，确立人伦生活的秩序。

This term, which comes from The Book of Changes, refers to the laws governing the movements of constellations and the change of weather. The term tianwen (天文) means the constant laws that govern the movements of celestial bodies, the rotation of the four seasons, the succession of day and night, and the change of weather. The ancient Chinese believed that both human relationships and all things in the universe are governed by the same laws, and so by observing and following the laws of constellations and seasons, people can establish social order.

▌引例

刚柔交错，天文也。文明以止，人文也。观乎天文，以察时变；观乎人文，以化成天下。 （《周易·彖上》）

It’s the law of heaven that the hard and soft interweave; it is a rule of humans that they should observe the rites and conduct restraint. By observing the movement of constellations, we can learn about the change of seasons; by observing development of human culture, we can enlighten the people and build a civilized society. (The Book of Changes)

本义指屋檐和栋梁，引申指空间和时间，及由无限空间和无限时间所构成的世界整体。“宇”指天地四方，也即是包括上、下、东、西、南、北的整个空间；“宙”指往古来今，也即是包括过去和未来的整个时间。“宇宙”在空间上可以无限扩展，在时间上可以无限延续。中国哲学以“宇宙论”指称探讨世界本体及世界发生发展进程的学问。

The original meaning of the term is the eave and beam of a house, while its extended meaning is time and space as well as the whole world composed of limitless time and space. The first character yu (宇) means heaven and earth as well as all the directions of north, south, east, west, the above, and the below. The second character zhou（宙）means all of time, the past, present, and future. Together, the term means infinite space and endless time. In Chinese philosophy, “theories of the universe” are concerned with the existence of the world in an ontological sense, and with its process of evolution. 

▌引例

宇之表无极，宙之端无穷。 （张衡《灵宪》）

Yu means space without limit; zhou represents time without end. (Zhang Heng: Law of the Universe)

“浑沌”又作“混沌”，有两种不同含义：其一，指天地分化形成以前宇宙浑然一体的状态。常以未分化之“气”言之。天地万物皆由“浑沌”分化演变而成。其二，特指《庄子》一则寓言中的中央之帝。中央之帝浑沌无七窍，被南海之帝儵（shū）和北海之帝忽凿开七窍而亡。庄子（前369？—前286）以此形象寓指人无知无识、无善恶彼我之分，与整个世界浑然一体的状态。

The term has two meanings. First, it refers to the state of one whole mass that existed before the universe took shape, often said to exist before qi (vital force) emerged. The multitude of organisms on earth all emanated from this state. Second, it refers to Chaos, king of the Central Region in a fable in Zhuangzi. According to the fable, Chaos had no eyes, nose, mouth or ears. Shu, king of the South Sea, and Hu, king of the North Sea, drilled seven apertures into Chaos and killed him. Zhuangzi （369？-286 BC）used this story to show the state of chaos of the world in which there is neither knowledge or wisdom, nor distinction between good and evil.

▌引例

说《易》者曰：“元气未分，浑沌为一。” （王充《论衡·谈天》）

Those who commented on The Book of Changes said, “Before qi (vital force) appeared, the world was in a state of formless chaos.” (Wang Chong: A Comparative Study of Different Schools of Learning)