"quality or condition of being flat or level," 1650s, from plane (adj.) + -ness.
Entries linking to planeness
plane adj.
"having the characteristics of a plane," 1560s, from French plan, from Latin planus "flat, level, even" (see plane (n.1)).
-ness
word-forming element denoting action, quality, or state, attached to an adjective or past participle to form an abstract noun, from Old English -nes(s), from Proto-Germanic *in-assu- (cognates: Old Saxon -nissi, Middle Dutch -nisse, Dutch -nis, Old High German -nissa, German -nis, Gothic -inassus), from *-in-, originally belonging to the noun stem, + *-assu-, abstract noun suffix, probably from the same root as Latin -tudo (see -tude).