a quadratic equation

Used other than figuratively or idiomatically: see 二, 枚, 目. (the second sheet or other flat thing) / a handsome male character, especially one that gets involved in a romance during the story

double standard

a Bactrian camel

derivative work

(inorganic chemistry) nitrogen dioxide

(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”)