Pinyin Sudoku 23 - Yi I

This is the first of four pinyin sudokus with "yi". The most prominent yi, "yī", which means "one" and is written by a simple horizontal stroke, is left out here. The funny thing is that another yi (which will appear in next week's sudoku), "亿（億）- yì", means "a hundred million"... just a slight difference of you pronounce it wrong... I always wonder and find it fascinating how the Chinese can express complicated or very special issues with just one character. There are various such "yi": It can mean e. g. "one's current attainment in learning or art" (诣（詣）- yì), "talk in sleep" (呓（囈）- yì), or even "to cut off the nose" (劓 - yì)...