simultaneous

adjective

si·​mul·​ta·​neous ˌsī-məl-ˈtā-nē-əs How to pronounce simultaneous (audio)
-nyəs,
 also  ˌsi-
1
: existing or occurring at the same time : exactly coincident
2
: satisfied by the same values of the variables
simultaneous equations
simultaneity noun
simultaneously
ˌsī-məl-ˈtā-nē-əs-lē How to pronounce simultaneous (audio)
-nyəs-
 also  ˌsi-
adverb
simultaneousness noun
Choose the Right Synonym for simultaneous

contemporary, contemporaneous, coeval, synchronous, simultaneous, coincident mean existing or occurring at the same time.

contemporary is likely to apply to people and what relates to them.

Abraham Lincoln was contemporary with Charles Darwin

contemporaneous is more often applied to events than to people.

contemporaneous accounts of the kidnapping

coeval refers usually to periods, ages, eras, eons.

two stars thought to be coeval

synchronous implies exact correspondence in time and especially in periodic intervals.

synchronous timepieces

simultaneous implies correspondence in a moment of time.

the two shots were simultaneous

coincident is applied to events and may be used in order to avoid implication of causal relationship.

the end of World War II was coincident with a great vintage year

Examples of simultaneous in a Sentence

The two gunshots were simultaneous. a simultaneous release of the movie and its soundtrack on CD
Recent Examples on the Web The alleged attack involved more than 420,000 nearly simultaneous access attempts from around the world, the secretary of state's office confirmed to USA TODAY after it was previously reported by WSB-TV, a broadcaster in Atlanta. Eric Lagatta, USA TODAY, 24 Oct. 2024 Dozens of stunt drivers from across Ohio converged on Cleveland late last month, setting off fireworks, blocking intersections, doing doughnuts and intimidating passing motorists in a series of simultaneous street takeovers that flummoxed local law enforcement. Sam Allard, Axios, 24 Oct. 2024 Those global efforts were at odds with the almost simultaneous transformation of the faith, domestically, into the religious right. Casey Cep, The New Yorker, 23 Oct. 2024 Commodity arbitrage involves the simultaneous or sequential buying and selling of commodities across different markets to profit from the price difference. Lee Ying Shan, CNBC, 23 Oct. 2024 See all Example Sentences for simultaneous 

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'simultaneous.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History

Etymology

borrowed from Medieval Latin simultāneus "occurring at the same time," from Latin simul "in company, together, at the same time" (going back to an apocopated neuter form of similis "having characteristics in common, like") + Medieval Latin -tāneus, as in instantāneus instantaneous, Late Latin momentāneus "momentary," spontāneus "voluntary, unconstrained, spontaneous" — more at similar

Note: The Dictionary of Medieval Latin from British Sources records one occurrence of simultāneus, in the Tractatus de logica of John Wycliffe. At the entry in that dictionary the word is parsed as from simultās "occurrence at the same time" (distinct from classical Latin simultās "state of animosity") + the suffix -āneus. This analysis is possible but seems less likely. Regarding the suffix -āneus see the etymology and note at spontaneous.

First Known Use

circa 1660, in the meaning defined at sense 1

Time Traveler
The first known use of simultaneous was circa 1660

Dictionary Entries Near simultaneous

Cite this Entry

“Simultaneous.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/simultaneous. Accessed 31 Oct. 2024.

Kids Definition

simultaneous

adjective
si·​mul·​ta·​neous ˌsī-məl-ˈtā-nē-əs How to pronounce simultaneous (audio)
-nyəs
1
: existing or occurring at the same time
2
: satisfied by the same values of the variables
simultaneous equations
simultaneously adverb
Etymology

from Latin simul "at the same time, together" and English -taneous (as in instantaneous) — related to assemble, ensemble

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