*plat-

*pelə-, Proto-Indo-European root meaning "flat; to spread."

It forms all or part of: airplane; dysplasia; ectoplasm; effleurage; esplanade; explain; explanation; feldspar; field; flaneur; floor; llano; palm (n.1) "flat of the hand;" palm (n.2) "tropical tree;" palmy; piano; pianoforte; plain; plan; planar; Planaria; plane (n.1) "flat surface;" plane (n.3) "tool for smoothing surfaces;" plane (v.2) "soar, glide on motionless wings;" planet; plani-; planisphere; plano-; -plasia; plasma; plasmid; plasm; -plasm; -plast; plaster; plastic; plastid; -plasty; Polack; Poland; Pole; polka; protoplasm; veldt.

It is the hypothetical source of/evidence for its existence is provided by: Greek plassein "to mold," plasma "something molded or created;" Latin planus "flat, level, even, plain, clear;" Lithuanian plonas "thin;" Celtic *lanon "plain;" Old Church Slavonic polje "flat land, field," Russian polyi "open;" Old English feld, Middle Dutch veld "field."

"a family, a tribe," especially, among the Highlanders of Scotland, a form of social organization consisting of a tribe holding land in common under leadership of a chieftain, early 15c., from Gaelic clann "family, stock, offspring," akin to Old Irish cland "offspring, tribe," both from Latin planta "offshoot" (see plant (n.)).

The Goidelic branch of Celtic (including Gaelic) had no initial p-, so it substituted k- or c- for Latin p-. The same Latin word in (non-Goidelic) Middle Welsh became plant "children."