The ten heavenly stems () or ten stems (Chinese: 十干; pinyin: shígān) are an ancient Chinese cyclic numeral system. They were first used for dates in the Shang Dynasty, and are now used with the twelve Earthly Branches in the Sexagesimal cycle in the Chinese calendar and in Chinese astrology. They are associated with Yin Yang and the Five Elements.

The Shang people had a myth in which there were ten suns, each of which appears in order in a ten-day cycle (旬; xǔn). The Heavenly Stems were the names of the ten suns. The kings of the Shang had characters of the Stems in their given names. Some historians think the ruling class of the Shang had ten clans, but it is not clear whether their society reflected the myth or vice versa. The association to Yin Yang and the Five Elements occurred later, after the collapse of the Shang Dynasty.

The Stems are still commonly used nowadays in China in counting systems similar to the way the alphabet is used in English, namely,

• Students' grades: with an additional Yōu (優 "Excellence") before Jiǎ.
• Choices on multiple choice exams, surveys, and etc.
• Vitamins' names (although currently, in this case, the ABC system is more popular)
• Organic chemicals' names (e.g. methanol: 甲醇, ethanol: 乙醇).

Japanese use the Stems as names in legal documents and contracts where English speakers would use A, B, C, etc.

See also

• Chinese numerals

External links

• Heavenly Stems and Earthly Branches - Hong Kong Observatory