Yin and yang Da Cidian") enter "yangyin" *陽陰. While "yang" and "yin" can occur together in context, "yangyin" is not synonymous with "yinyang". The linguistic term "irreversible binomial" refers to a collocation of two words A-B that cannot be idiomatically reversed as B-A, for example, English "cat and mouse" (not *"mouse and cat") and "friend or foe" (not *"foe or friend"). 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, for example, "tiandi" 天地 "heaven and earth" and "nannü" 男女 "men and women". "Yinyang" meaning "dark and
Yin and yang light; female and male; moon and sun", however, is an exception. Scholars have proposed various explanations for why "yinyang" violates this pattern, including "linguistic convenience" (it is easier to say "yinyang" than "yangyin"), the idea that "proto-Chinese society was matriarchal", or perhaps, since "yinyang" first became prominent during the late Warring States period, this term was "purposely directed at challenging persistent cultural assumptions". Needham discusses Yin and Yang together with Five Elements as part of the School of Naturalists. He says that it would be proper to begin with Yin and Yang before Five Elements because the former: "lay, as