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Toponymy

Many Chinese place names or toponyms contain the word yang "sunny side" and a few contain yin "shady side". In China, as elsewhere in the Northern Hemisphere, sunlight comes predominantly from the south, and thus the south face of a mountain or the north bank of a river will receive more direct sunlight than the opposite side.

Yang refers to the "south side of a hill" in Hengyang 衡陽, which is south of Mount Heng 衡山 in Hunan province, and to the "north bank of a river" in Luoyang 洛陽, which is located north of the Luo River 洛河 in Henan.

Similarly, yin refers to "north side of a hill" in Huayin 華陰, which is north of Mount Hua 華山 in Shaanxi province.

In Japan, the characters are used in western Honshu to delineate the north-side San'in region 山陰 from the south-side San'yō region 山陽, separated by the Chūgoku Mountains 中国山地.