a combining form meaning “having parts or units” of the number specified by the initial element, occurring originally in loanwords from Latin (duplex; quadruplex); recent English coinages ending in -plex, especially denoting structures with a given number of dwelling units, are probably in part new formations with this suffix and in part based on the noun complex: fourplex; eightplex; Cineplex; Metroplex.
Origin
< Latin-plex, -plic- (akin to plicāre to fold, bend, plectere to plait, braid; see -fold) + -s nominative singular ending