interplanetary (adj.)
1690s, "existing between planets," from inter- "between" + planet + -ary. In reference to travel between planets, attested from 1897. Boyle and Locke both used intermundane in the same sense; the Roman Epicureans had intermundia (neuter plural) for "spaces between the worlds" (translating Greek metakosmia).
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A living prefix in English from 15c. and used with Germanic as well as Latinate words. Spelled entre- in French; most words borrowed into English in that form were re-spelled 16c. to conform with Latin except entertain, enterprise. In Latin, spelling shifted to intel- before -l-, hence intelligence, etc.
late Old English planete, in old astronomy, "star other than a fixed star; star revolving in an orbit," from Old French planete (Modern French planète) and directly from Late Latin planeta, from Greek planētēs, from (asteres) planētai "wandering (stars)," from planasthai "to wander," a word of uncertain etymology.
Perhaps it is from a nasalized form of PIE root *pele- (2) "flat; to spread," on the notion of "spread out," "but the semantics are highly problematic," according to Beekes, who notes the similarity of meaning to Greek plazein "to make devious, repel, dissuade from the right path, bewilder," but adds, "it is hard to think of a formal connection."
So called because they have apparent motion, unlike the "fixed" stars. Originally including also the moon and sun but not the Earth; modern scientific sense of "world that orbits a star" is from 1630s in English. The Greek word is an enlarged form of planes, planetos "who wanders around, wanderer," also "wandering star, planet," in medicine "unstable temperature."
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Dictionary entries near interplanetary
interpellation
interpenetrate
interpenetration
interpersonal
interphase
interplanetary
interplay
Interpol
interpolate
interpolation
interpolator
