letter challenging someone to a duel

base / be based on

a male given name / a surname

Alternative form of 元 / (chemistry) a group; a radical

foundation; base; basis / (chemistry) a group; a radical

counter for grounded things (e.g. pyramids, electric power plants, wells, toro (Japanese traditional lantern), tombs) / counter for wooden grave tablets (卒塔婆 (sotoba))

base

gender role

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

(chemistry) organic solvent