Noun
One of the ten terms used in East Asian cultures to represent
(historical or astrology) A day of the traditional ten-day week.
(mythology) One of the ten suns thought to appear in succession on its appointed day of the traditional week.
(historical religion) The ancestor venerated with a ritual on the appointed day of the traditional week.
(formal) An ordinal, used in similar contexts to Roman numerals in English numbering and outlining.
Source: en.wiktionary.org