simultaneous

American  

[sahy-muhl-tey-nee-uhs, sim-uhl-] / ˌsaɪ məlˈteɪ ni əs, ˌsɪm əl- /

adjective

1. existing, occurring, or operating at the same time; concurrent: simultaneous translation.

   simultaneous movements;

   simultaneous translation.

   Synonyms:

   coincident, synchronous

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simultaneous British  

/ ˌsaɪməltəˈniːɪtɪ, ˌsɪməltəˈniːɪtɪ, ˌsaɪməlˈteɪnɪəs, ˌsɪməlˈteɪnɪəs /

adjective

1. occurring, existing, or operating at the same time; concurrent

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noun

1. Sometimes shortened to: simul.  chess a display in which one player plays a number of opponents at once, walking from board to board

Other Word Forms

• simultaneity
  noun
• simultaneousness
  noun
• unsimultaneousness
  noun
• nonsimultaneous
  adjective
• unsimultaneous
  adjective
• simultaneously
  adverb

Etymology

Origin of simultaneous

First recorded in 1650–60; from Latin simul “together” ( see similar) + (instan)taneous

Explanation

The adjective simultaneous describes something that is done at the same time as something else. "The teachers all assigned simultaneous projects to the students that week. The kids were grumbling and sleep-deprived due to the grind." The Latin root of simultaneous is simul, which also means "at the same time." One way to remember this word is to think of simulcast programs that are simultaneously available through different television networks, radio stations or Web sites — so you can catch that concert on TV while your friend is listening to it on his car radio.

Example Sentences

Also helpful: the Bank of Japan’ decision to raise interest rates by 25 basis points this week to 1% and the simultaneous decision to halt its government bond purchases starting in April 2027.

From Barron's • Jun. 19, 2026

That bumpy two weeks kicks off Thursday with the massive simultaneous expirations of stock options, stock-index futures and stock-index options, coming a day earlier than usual due to the Juneteenth holiday on Friday.

From MarketWatch • Jun. 18, 2026

Other simultaneous downloads swept up episodes of “The Big Bang Theory” and “Ted Lasso” out of order, though a putative human user would probably have downloaded them sequentially.

From Los Angeles Times • Jun. 18, 2026

Tickets must be purchased online for specific time slots, the number of simultaneous visitors is capped at 1,500 and a daily morning “quiet hour” was recently introduced to facilitate prayer and contemplation.

From The Wall Street Journal • Jun. 7, 2026

But there was Dr. Max Pavey up on the stage—the man Bobby had played in a simultaneous exhibition three years previously—ready to play for his country.

From "Endgame" by Frank Brady

Related Words

• concurrent