甲乙丙 - the heavenly or celestial stems
The ten Celestial Stems are a counting system first used over 3000 years ago, when they were used for marking
weeks of ten days each. The symbols were then used in various other contexts for counting or reference.
Today, the Celestial Stems are still used for counting - 甲乙丙 (こうおつへい) corresponds roughly with the English 'ABC' - and
they are combined with the Earthly Branches (Chinese zodiac) in Taoism.
For more information on the Celestial Stems, see the
Wikipedia entry.
For more learning tools and games, click here.