Playing cards (simplified Chinese: 纸牌; traditional Chinese: 紙牌; pinyin: zhǐpái) were most likely invented in China during the Southern Song dynasty (1127–1279). They were certainly in existence by the Mongol Yuan dynasty (1271-1368). Chinese use the word pái (牌), meaning "plaque", to refer to both playing cards and tiles. Many early sources are ambiguous, and do not specifically refer to paper pái (cards) or bone pái (tiles). In terms of game play, however, there is no difference; both serve to hide one face from the other players with identical backs. Card games are examples of imperfect information games as opposed to Chess or Go.