I. ˈdü-ˌpleks also ˈdyü- adjective
Etymology: Latin, from duo two + -plex -fold — more at two , -fold
Date: 1567
1.
a. : having two principal elements or parts : double , twofold
b. : having two complementary polynucleotide strands of DNA or of DNA and RNA
2. : allowing telecommunication in opposite directions simultaneously
II. transitive verb
Date: 1833
: to make duplex
III. noun
Date: 1922
: something duplex: as
a. : a 2-family house
b. : duplex apartment
c. : a duplex molecule of DNA or of RNA and DNA