double torture; double pain; double hardship; double whammy
double circle (indicating "very good" on a piece of school work)
dual personality; split personality
twofold and threefold; doubled and redoubled
dual structure; double structure
instrumental duet; instrumental duo
double helix (structure of DNA)
duality; dual nature; duplexity; two-fold character
double-glazed window; double window; storm window
someone with a dual personality
double star; visual double
(illegal) dual bookkeeping; two sets of books
dual nationality; dual citizenship
double glazing; double-paned glass
dual monarchy; Austria-Hungary; Austro-Hungarian Empire
double weave; double cloth
redundant keigo (i.e. improper use of the -rareru honorific form together with an honorific verb such as ossharu)
double printing; superimposition; superimposing
two prices (for the same product); dual pricing
managing data from two locations; dual control; dual custody
double jeopardy; double punishment; double penalty
double standard of morality
dual attachment concentrator
issuing (the same receipt) twice; issuing duplicate (receipts)
deuterium; heavy hydrogen