Vocabulary

secondary memory

quadratic equation

choosing between two things; two choices

two kinds

two weeks; fortnight

24 solar stems (terms used to denote the changing of the seasons); 24 divisions of the Chinese solar year

many-fold

(one's) 20s; twenties

house mouse (Mus musculus)

radish (Raphanus sativus var. sativus)

dual diplomacy

double chin

jacketed kettle; double boiler

bigamy

dual nationality; dual citizenship

double exposure

vocal duet

double printing; superimposition; superimposing

bifocal

double weave; double cloth

doppelganger

dual personality; split personality

double star; visual double

double life

double duty

double-glazed window; double window; storm window

double bottom (ship, trunk, etc.); false bottom; double sole; double hull

second mortgage

double standard of morality

double negative

diphthong

double blind trial; double blind test

double helix (structure of DNA)

double exposure

square (of a number); multiplying (a number) by itself; second power

square root

two-color printing; two-colour printing

postscript; PS

binary

in no way