• synonyms


[sahy-muhl-tey-nee-uhs, sim-uhl-]
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  1. existing, occurring, or operating at the same time; concurrent: simultaneous movements; simultaneous translation.
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Origin of simultaneous

1650–60; < Latin simul together (see similar) + (instan)taneous
Related formssi·mul·ta·ne·ous·ly, adverbsi·mul·ta·ne·ous·ness, si·mul·ta·ne·i·ty [sahy-muhl-tuh-nee-i-tee, sim-uhl-] /ˌsaɪ məl təˈni ɪ ti, ˌsɪm əl-/, nounnon·si·mul·ta·ne·ous, adjectivenon·si·mul·ta·ne·ous·ly, adverbun·si·mul·ta·ne·ous, adjectiveun·si·mul·ta·ne·ous·ly, adverbun·si·mul·ta·ne·ous·ness, noun

Synonyms for simultaneous

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Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Related Words for simultaneity

unanimity, synchronism, synchroneity, simultaneity

Examples from the Web for simultaneity

Historical Examples of simultaneity

  • Twins they were in simultaneity of birth, but not in likeness of growth.

    A Century of Science and Other Essays

    John Fiske

  • We have not a direct intuition of simultaneity, nor of the equality of two durations.

    Major Prophets of To-Day

    Edwin E. Slosson

  • This simultaneity and concurrency are central tenets of imposing Shock and Awe.

    Shock and Awe

    Harlan K. Ullman

  • One may not appear twice in simultaneity upon the Time-scroll.

  • He was interested by the celerity, the simultaneity of his impressions, his reflections.

    Literature and Life

    William Dean Howells

British Dictionary definitions for simultaneity


  1. occurring, existing, or operating at the same time; concurrent
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  1. chess a display in which one player plays a number of opponents at once, walking from board to boardSometimes shortened to: simul
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Derived Formssimultaneously, adverbsimultaneousness or simultaneity (ˌsɪməltəˈniːɪtɪ, US ˌsaɪməltəˈniːɪtɪ), noun

Word Origin for simultaneous

C17: formed on the model of instantaneous from Latin simul at the same time, together
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for simultaneity


1650s, from simultaneous + -ity.

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1650s, from Medieval Latin simultaneus, perhaps from simultim "at the same time," extended from Latin simul "at the same time" (see similar (adj.)), or from simul with ending abstracted from Late Latin spontaneus, where the -t- is organic. Related: Simultaneously.

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Online Etymology Dictionary, © 2010 Douglas Harper