interplanetary

Etymology

It is formed from English inter- + planetary, with the prefix meaning "between".^{[2][3][4][5][6]} Etymonline notes that Boyle and Locke also used intermundane in the same sense, and that the Roman Epicureans spoke of Latin intermundia (“spaces between the worlds”), translating a Greek term.^[6]

Earliest recorded meaning

Situated between the planets: before 1691, in Robert Boyle's General History of the Air (published 1692).^[2][4] Etymonline gives the 1690s and Dictionary.com 1685–95.^[6][5]

Semantic evolution

From the sense of space lying between the planets the word extended to anything existing or operating between them.^[2][3] Its use for travel between planets is recorded from 1897,^[6] and the OED now includes it in the definition.^[2]

Timeline

• before 1691 – situated between the planets, in Boyle.^[2][4]
• 1897 – of or relating to travel between planets.^[6]

Meanings

Adjective

1. Existing, happening or operating between the planets: interplanetary dust.^[3][7][8][2]
2. Relating to travel between planets: an interplanetary probe.^[2]

Related words

• planetary
• planet
• intermundane

References

1. ^ a b c Wiktionary, the free dictionary, https://en.wiktionary.org
2. ^ a b c d e f g Oxford English Dictionary Online (accessed March 2026), Oxford: Oxford University Press
3. ^ a b c Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
4. ^ a b c Barnhart, Robert K. (1988), The Barnhart Dictionary of Etymology
5. ^ a b Dictionary.com Unabridged (2016), based on the Random House Unabridged Dictionary, New York: Random House
6. ^ a b c d e Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
7. ^ Collins English Dictionary (2023), Glasgow: HarperCollins
8. ^ The American Heritage Dictionary of the English Language (1992), 3rd ed., Boston: Houghton Mifflin