Meaning

adjective allowing communication in only one direction at a time, or in telegraphy allowing only one message over a line at a time

adjective having only one part or element

originThe adjective is a learned borrowing from Latin simplex (“plain, simple; single”). The first part, sim-, comes from Proto-Indo-European *sem-, *sm̥- (“one; together”). The second part, -plex, may be from *pleḱ- (“to weave”). The noun is derived from the adjective. The plural forms simplices and simplicia are learned borrowings from Latin simplicēs (masculine or feminine) and simplicia (neuter),…

Etymology from Wiktionary, CC BY-SA 3.0