adj
instantaneous
ihns-tuhn-TAY-nee-uhs
adj
1
Happening so fast it seems to occur at once, with no noticeable delay.
"The camera flash and the shutter click were almost instantaneous."
"Light travel over short distances feels instantaneous to the human eye."
How to Use Instantaneous
Learner’s notesIn plain EnglishOccurring in essentially zero time.
When to use it
More formal and technical-sounding than "instant" — common in science and engineering writing.
Common pairings
instantaneous reaction
instantaneous effect
nearly instantaneous
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The camera flash and the shutter click were almost _____.
Etymology
From New Latin instantaneus, built on the same Latin root as instant.