abbreviation of 平(へい)安(あん)時(じ)代(だい) (Heian jidai, “the Heian period of Japanese history”)

age, era, period (of time) / the times, spirit of the age / antiquity / a time in one's life, one's days (in college etc.)

history / the study of history

letter challenging someone to a duel

Japan

(archaic) Japan

Short for 日本国 (Nihon-koku): Japan (a country and archipelago in East Asia) / a surname

gender role

(linguistics) "role language": unique language usage serving as a marker of social identity in fictional speech

codification, the act of putting something into writing (said particularly of rules or decisions)