Nouns

(n)duplex house, duplex, semidetached housea house with two units sharing a common wall
(n)duplex apartment, duplexan apartment having rooms on two floors that are connected by a staircase

Verbs

(v)duplexchange into a duplex

Adjectives

(s)duplex(used technically of a device or process) having two parts“a duplex transaction”
(s)duplexallowing communication in opposite directions simultaneously“duplex system”, “duplex telephony”