First of the ten Heavenly Stems; used to indicate the first position in a sequence or rank, often equivalent to "A" or "I" in English lists; ancient Chinese compass point (75°)

(bound form) sulfur; a nonmetallic chemical element with the symbol S

Chemical compound of nitrogen and hydrogen that is a colorless gas with a pungent smell; commonly used in fertilizers and refrigerants.

acid, a chemical compound that releases hydrogen ions in water