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" "heaven and earth" and "nannü" "men and women". "Yinyang" meaning "dark and 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".