simultaneous

Etymology

The OED takes it from a Latin type borrowed from Medieval Latin *simultāneus, formed on Latin simul (“at the same time”), probably after mōmentāneus (“momentary”);^[2][3][4][5] Etymonline also derives it from Medieval Latin, perhaps through the extended form simultim (“at the same time”), or with the ending of Late Latin spontāneus.^[6] Barnhart, the American Heritage Dictionary and Merriam-Webster's Collegiate instead take it as probably formed in English from simul and the ending -taneous of instantaneous and spontaneous.^[7][8][9] The Medieval Latin form is recorded by Du Cange only in the sense "simulated".^[2] Simul is related to similis (“like, similar”),^[6][7][10] the source of similar, and goes back to Proto-Indo-European *sem- (“one, as one”).^[8] French has simultané from 1740.^[2]

Earliest recorded meaning

Existing or happening at the same time: before 1660, in the works of H. Hammond.^[2][3][7] Etymonline dates it to the 1650s.^[6]

Semantic evolution

Blount's dictionary (1656), citing it from L'Estrange, wrongly linked it with Latin simultas and explained it as secretly hating behind a feigned face, and Phillips (1658) repeated the mistake; in 1678 Marvell mocked it as an "elegant term" of his opponent's own making.^[2] Johnson (1755) defined it as acting together, existing at the same time.^[11] Later it gained technical uses: in mathematics, of equations satisfied by the same values (1816),^[2][12] in chess, of a display in which one player meets several opponents at once (1883),^[2][13] and of interpretation done while the speaker is talking (1958).^[2] Mark Twain back-formed a verb simultane in 1880.^[6]

Timeline

• 1650s – existing or occurring at the same time (Etymonline).^[6]
• before 1660 – the same sense, in H. Hammond's works.^[2][3]
• 1656 – misexplained in Blount's Glossographia.^[2]
• 1816 – mathematics, simultaneous equations.^[2]
• 1883 – chess, games played against several opponents at once.^[2]
• 1958 – simultaneous interpretation.^[2]

Meanings

Adjective

1. Happening, existing or done at the same time; concurrent: The two bells gave simultaneous chimes at noon.^{[13][3][12][2]}
2. (mathematics) Of equations, satisfied by the same values of the variables.^[12][9][2]
3. Of interpretation or translation, given while the speaker is still talking.^[2]

Noun

1. (chess) A display in which one player plays several opponents at once, moving from board to board.^[13][2]

Word family

• simultaneously
• simultaneity
• simultaneousness
• nonsimultaneous
• unsimultaneous

Related words

• similar
• same
• simulcast
• instantaneous
• spontaneous
• momentaneous

References

1. ^ a b Wiktionary, the free dictionary, https://en.wiktionary.org
2. ^ a b c d e f g h i j k l m n o p q Oxford English Dictionary Online (accessed March 2026), Oxford: Oxford University Press
3. ^ a b c d Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
4. ^ Shorter Oxford English Dictionary on Historical Principles (2002), 5th ed., ed. William R. Trumble and Angus Stevenson, Oxford: Oxford University Press
5. ^ Klein, Ernest. A Comprehensive Etymological Dictionary of the English Language. 2 vols. Amsterdam: Elsevier, 1966–1967.
6. ^ a b c d e Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
7. ^ a b c Barnhart, Robert K. (1988), The Barnhart Dictionary of Etymology
8. ^ a b The American Heritage Dictionary of the English Language (online 2024), 5th ed., Boston: Houghton Mifflin Harcourt
9. ^ a b Merriam-Webster's Collegiate Dictionary (2003), 11th ed., Springfield, Mass.: Merriam-Webster
10. ^ Weekley, Ernest (1921), An Etymological Dictionary of Modern English, London: John Murray
11. ^ Johnson, Samuel (1755), A Dictionary of the English Language, London; 4th ed. 1773; Johnson's Dictionary Online, ed. Beth Rapp Young et al.
12. ^ a b c The American Heritage Dictionary of the English Language (1992), 3rd ed., Boston: Houghton Mifflin
13. ^ a b c Collins English Dictionary (2023), Glasgow: HarperCollins