[4] In Chinese cosmology, the universe creates itself out of a primary chaos of material energy, organized into the cycles of yin and yang, form and matter.

'Yin' is retractive, passive and contractive in nature, while 'yang' is repelling, active and expansive in principle; this dichotomy in some form, is seen in all things in nature—patterns of change and difference.

For example, biological and seasonal cycles, evolution of the landscape over days, weeks, years and eons (with the original meaning of the words being the north-facing shade and the south-facing brightness of a hill), gender (female and male), as well as the formation of the character of individuals and the grand arc of sociopolitical history in disorder and order.

[5] Taiji is a Chinese cosmological term for the "Supreme Ultimate" state of undifferentiated absolute and infinite potential, the oneness before duality, from which yin and yang originate.

This duality, as a unity of opposites, lies at the origins of many branches of classical Chinese science, technology and philosophy, as well as being a primary guideline of traditional Chinese medicine,[7] and a central principle of different forms of Chinese martial arts and exercise, such as baguazhang, tai chi, daoyin, kung fu and qigong, as well as appearing in the pages of the I Ching and the famous Taoist medical treatise called the Huangdi Neijing The notion of duality can be found in many areas, such as Communities of Practice.

The term "dualistic-monism" or dialectical monism has been coined in an attempt to express this fruitful paradox of simultaneous unity and duality.

[citation needed] In Taoist metaphysics, distinctions between good and bad, along with other dichotomous moral judgments, are perceptual, not real; so, the duality of yin and yang is an indivisible whole.

In the ethics of Confucianism on the other hand, most notably in the philosophy of Dong Zhongshu (c. 2nd century BC), a moral dimension is attached to the idea of yin and yang.

yin < *ʔəm compares with Burmese ʔumC 'overcast', 'cloudy', Adi muk-jum 'shade', and Lepcha so'yǔm 'shade'; it is probably cognate with Chinese àn < *ʔə̂mʔ 黯; 'dim', 'gloomy' and qīn < *khəm 衾; 'blanket'.

To this word-family, Unger also includes 炳; bǐng < *pl(j)aŋʔ 'bright';[15] however Schuessler reconstructs 炳; bǐng's Old Chinese pronunciation as *braŋʔ and includes it in an Austroasiatic word family, besides 亮; liàng < *raŋh 爽; shuǎng < *sraŋʔ 'twilight of dawn'; míng < *mraŋ 明 'bright', 'become light', 'enlighten'; owing to "the different OC initial consonant which seems to have no recognizable OC morphological function".

[17] Yin 陰 or 阴—Noun: ① [philosophy] female/passive/negative principle in nature, ② Surname; Bound morpheme: ① the moon, ② shaded orientation, ③ covert; concealed; hidden, ④ vagina, ⑤ penis, ⑥ of the netherworld, ⑦ negative, ⑧ north side of a hill, ⑨ south bank of a river, ⑩ reverse side of a stele, ⑪ in intaglio; Stative verb: ① overcast, ② sinister; treacherousYang 陽 or 阳—Bound morpheme: ① [Chinese philosophy] male/active/positive principle in nature, ② the sun, ③ male genitals, ④ in relief, ⑤ open; overt, ⑥ belonging to this world, ⑦ [linguistics] masculine, ⑧ south side of a hill, ⑨ north bank of a riverThe compound yinyang 陰陽 means "yin and yang; opposites; ancient Chinese astronomy; occult arts; astrologer; geomancer; etc."

In Chinese philosophy, the feminine or negative principle (characterized by dark, wetness, cold, passivity, disintegration, etc.)

of the two opposing cosmic forces into which creative energy divides and whose fusion in physical matter brings the phenomenal world into being.

as yin-yang symbol, a circle divided by an S-shaped line into a dark and a light segment, representing respectively yin and yang, each containing a 'seed' of the other.

of the two opposing cosmic forces into which creative energy divides and whose fusion in physical matter brings the phenomenal world into being.

[23] Similarly, the usual pattern among Chinese binomial compounds is for positive A and negative B, where the A word is dominant or privileged over B.

He says that it would be proper to begin with yin and yang before Five Elements because the former: "lay, as it were, at a deeper level in Nature, and were the most ultimate principles of which the ancient Chinese could conceive.

Needham concludes "There can be very little doubt that the philosophical use of the terms began about the beginning of the 4th century, and that the passages in older texts which mention this use are interpolations made later than that time.

"[24] Yin and yang are a concept that originated in ancient Chinese philosophy that describes how opposite or contrary forces may create each other by their comparison and are to be seen as actually complementary, interconnected, and interdependent in the natural world, and how they may give rise to each other as they interrelate to one another.

[25][26] In Daoist philosophy, dark and light, yin and yang, arrive in the Tao Te Ching at chapter 42.

In traditional Chinese medicine, one's health is directly related to the balance between yin and yang qualities within them.

[31] The technology of yin and yang is the foundation of critical and deductive reasoning for effective differential diagnosis of disease and illnesses within Taoist influenced traditional Chinese medicine.

[citation needed] The principle of yin and yang is represented by the Taijitu (literally "Diagram of the Supreme Ultimate").

In terms of the art of attack and defense then, in the context of the changes of full and empty, one is constantly internally latent, to not outwardly expressive, as if the yin and yang of Taiji have not yet divided apart.'