duplex

Concise Oxford English Dictionary © 2008 Oxford University Press:
duplex /ˈdjuːplɛks/

▶noun

• 1 N. Amer. a residential building divided into two apartments.

  ■ a flat on two floors.

  ■ chiefly N. Amer. & Austral. a semi-detached house.

• 2 Biochemistry a double-stranded polynucleotide molecule.

▶adjective

• 1 having two parts.

• 2 (of a printer) capable of printing on both sides of the paper.

• 3 allowing the transmission of two signals simultaneously in opposite directions.

– origin C16 (as adj.): from L. duplex, duplic-, from duo ‘two’ + plicare ‘to fold’.