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plane

/pleɪn/

Flat surface, level, aircraft, or smoothing tool

From Latin, ultimately Proto-Indo-European plane (flat).

noun
verb
adjective
plane
Proto-Indo-European
Verified
*pla-no-
reconstructed
Flat, spread out; a suffixed form of *pele- “flat; to spread”.

from PIE *pla-no- (source also of Lithuanian plonas "thin;" Celtic *lanon "plain;" perhaps also Greek pelanos...

Latin
Verified
plānus; plānum
“Flat, level, plain”; plānum became the noun “flat surface” or “plane.”

from Latin planum "flat surface, plane, level, plain," noun use of neuter of adjective planus "flat, level, even,...

+1 more source
Late Latin
Verified
plāna
“Planing tool,” a related technical sense.

from Late Latin plāna (“planing tool”).

Middle English
Verified
plane, plaine
Inherited or borrowed forms referring to a flat surface or planing tool; later specialized geometrically.

from Middle English plane, plaine

Modern English
plane

Picture a Roman looking across a perfectly level patch of ground and calling it plānus—flat, even, plain. Latin turned that adjective into plānum, literally “the flat thing,” and centuries later English borrowed plane for geometry, partly to keep the mathematical sense apart from plain. The family has some wonderfully unexpected relatives: explain originally meant to “flatten out” an idea so the mind could see it clearly, while Spanish llano and Italian piano preserve the same flat-and-level ancestry. A plane was also a carpenter’s tool for shaving wood into a smooth surface, so the word moved from landscape to geometry to workshop. And then, in modern popular culture, Samuel L. Jackson’s furious snake-filled aircraft transformed “plane” into the setting for one of cinema’s most memorable exclamations—proof that even a word meaning “flat surface” can end up airborne.

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