(linguistics) doublet

going back to sleep (e.g. after waking up in the morning)

(idiomatic) unhesitatingly without dispute

(linguistics) diphthong

2-step authentication

a digastric muscle

(grammar) The Classical Japanese bigrade verb conjugation class, consisting of the two subclasses of 上(かみ)二(に)段(だん)活(かつ)用(よう) (kami nidan katsuyō, “upper-bigrade conjugation”) and 下(しも)二(に)段(だん)活(かつ)用(よう) (shimo nidan katsuyō, “lower-bigrade conjugation”)

double-pane window, found especially in Hokkaido and Tōhoku as cold-proofing

a Classical Japanese adjective with シク活用 (shiku-katsuyō, “shiku-inflection”)

double dipping