Instantaneous

Happening or done in an instant; immediate, with no perceptible delay.

adjective

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Imagine This

Imagine flipping a light switch and the room becomes fully lit in a flash; there is no waiting or gradual brightening—everything happens instantaneously.

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Sounds Like

in-STAN-tee-uh-nəs

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Looks Like

looks like 'instant' with the suffix '-aneous'

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Remember This

Used for reactions, changes, or measurements that occur at a single moment. Common in science contexts (instantaneous velocity) and everyday speech (an instantaneous decision).

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Other Forms

instantaneouslyadverb

instantaneousnessnoun

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Connect With

immediate, instant, rapid, sudden, prompt, instantaneous velocity

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Note

Do not use for gradual changes or long processes. Distinguish from 'instant' as a noun or time moment; 'instantaneous' emphasizes no delay.

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Study Deeper

Examples

The reaction was instantaneous once the catalyst was added.
In physics, the velocity at a specific moment is called instantaneous velocity.

Synonyms

immediatepromptrapidswiftsudden

Antonyms

delayedgradualprolonged

Etymology

From instant + the suffix -aneous. The base 'instant' derives from Medieval Latin instantus, from Latin instāns, present participle of instāre 'to stand at hand' or 'to stand near'; the suffix -aneous forms an adjective meaning 'having the quality of' or 'relating to'.

Mnemonic

Mnemonic: Instant + -aneous literally says it all—something happening in an instant. Visualize a stopwatch that flashes a complete scene in the blink of an eye to remember that it means immediate.