Having a given number of parts or units.
[Latin plicare, to fold.]
This ending can refer to numerical multiples: duplex, something having two parts; multiplex, consisting of many elements in a complex relationship; simplex (Latin, literally ‘single’, variant of simplus, simple), composed of or characterized by a single part or structure; googolplex, equivalent to ten raised to the power of a googol, itself an invented word meaning ten raised to the power of a hundred (10100).
In addition, duplex can mean a residential building divided into two apartments, or two houses with a common wall (semi-detached in British usage), and a multiplex can be a cinema with several separate screens. This meaning, of a group of similar buildings or facilities on the same site, derives from one sense of complex, which comes from the same Latin stem.
Other examples—particularly common in North America—are triplex, a building divided into three self-contained residences; fourplex (also quadraplex and quadriplex), a building divided into four such residences; Cineplex, a trade name for a cinema with several separate screens; and, by extension, metroplex, a very large metropolitan area, especially one which is an aggregation of two or more cities. Several of these were originally blends (Cineplex from cinema and complex, for example), but -plex seems now to be established as a combining form in this sense.