Translation guide
Describes something happening extremely quickly, almost instantaneously. Japanese uses various adverbs, onomatopoeia, and set phrases to convey this sense of sudden speed.
To say that something happens immediately or in the blink of an eye.
Literally 'one moment'. Used as an adverb with で or に to mean 'in an instant'. Very common and natural.
He solved the problem in a flash.
It disappeared in a flash.
Literally 'in the time it takes to blink'. A very natural and common phrase for something happening in a flash.
The preparations were done in a flash.
Means 'in the time it takes to say "ah"', i.e., before you know it. Very common in spoken Japanese.
He finished eating in a flash.
An adverb meaning 'in no time', 'at once'. Slightly more literary or emphatic than すぐに.
A crowd gathered in a flash.
Means 'immediately' or 'right away'. While not as vivid as 'in a flash', it is the most common way to express quick action.
I'll be back in a flash.
To emphasize that something appears or changes so quickly it's almost like magic.
Onomatopoeic adverb suggesting a sudden, bright flash or quick action. Often used for lights, ideas, or quick movements.
The light came on in a flash.
A good idea came to me in a flash.
Onomatopoeic adverb for a swift, smooth movement or change. Implies something done quickly and cleanly.
To compare the speed to lightning or a flash of light.
All three mean 'in a flash', but 一瞬 emphasizes the brevity of the moment itself, while あっという間に and 瞬く間に emphasize the subjective feeling that time passed quickly. あっという間に is more colloquial; 瞬く間に is slightly more formal or literary.
Do not translate 'in a flash' literally as フラッシュの中で. This would mean 'inside a camera flash' and is not idiomatic.
The thief disappeared in a flash.
He stood up in a flash.