simultaneous

adjective

si·​mul·​ta·​neous ˌsī-məl-ˈtā-nē-əs 

-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

ˌsī-məl-tə-ˈnē-ə-tē

-ˈnā-

 also  ˌsi-

noun

simultaneously

ˌsī-məl-ˈtā-nē-əs-lē 

-nyəs-

 also  ˌsi-

adverb

simultaneousness noun

Synonyms

• coetaneous
• coeval
• coexistent
• coexisting
• coextensive
• coincident
• coincidental
• concurrent
• contemporaneous
• contemporary
• coterminous
• synchronic
• synchronous

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

At the product launch, Xiaomi founder Lei Jun described how the Mix Fold 4 could handle simultaneous translation with one language on each side of the screen. —Evelyn Cheng, CNBC, 19 July 2024

When a future Navigator was previewed as a concept car some years back, it was shown with a giant, birdlike gull wing door on either side, each of which folded up above the roof, exposing a giant opening that provided simultaneous access to the first two of the vehicle’s three rows. —Brett Berk, Architectural Digest, 16 Aug. 2024

This year's cicada emergence was a double whammy of insects, with two groups of periodical cicadas that only come out of the ground every 13 or 17 years making a simultaneous appearance. —Li Cohen, CBS News, 15 Aug. 2024

Join 5 others in the comments View Comments During the Games’ first week, Peacock streamed up to 60 simultaneous live events and up to 300 live events per day, the company said, culminating in more than 3,200 live events over the course of the Games, a major technological feat for the streamer. —Liam Reilly, CNN, 13 Aug. 2024

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

Kids Definition

simultaneous

adjective

si·​mul·​ta·​neous ˌsī-məl-ˈtā-nē-əs 

-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