Dumb. Speechless, mute, silent, still, inarticulate.
Ant. Talkative, chatty, loquacious.
Duplicate. Copy, counterpart, facsimile, imitation, likeness, replica, reproduction, double, transcript.
Ant. Original, pattern, prototype, archetype, model.
Duplicity. Deceit, deception, circumvention, guile, artifice, hypocrisy, fraud, dishonesty.
Ant. Candor, straightforwardness, frankness, sincerity, honesty.
Duration. Continuance, term, period, protraction, prolongation (in time).
Ant. Brevity, momentariness; infinity, eternity.
Duty. Office, responsibility, obligation, function, business, accountability, right, righteousness.
Ant. Immunity, freedom, license, exemption, dispensation.