initial cycle character C1 the first of two characters required to designate a lunar cycle in a Chinese-Japanese-Korean date phrase described by PS-RULE ODP2: there are ten possible ideographs in use: 1) 甲, 2) 乙, 3) 丙, 4)丁, 5) 戊, 6) 己, 7) 庚, 8) 辛, 9) 壬, 10) 癸