noun, noun which may take the genitive case particle 'no'
Refers to an extremely short period of time, often used in contexts emphasizing speed or suddenness. Can be used as a noun or adjectivally with の.
彼の表情は瞬時に変わった。
His expression changed in an instant.
瞬時の判断が求められる場面だった。
It was a situation that required a split-second decision.