一瞬|いっしゅんisshun[0]heiban (flat)

1. noun, adverbinstant; moment; for an instant
   それは私にとってはらはらする一瞬いっしゅんだった。↗

   It was a nervous moment for me.

• Synonym瞬間しゅんかんNeutralCan mark the very moment something happens, as in 「見た瞬間」; 「一瞬」 stresses how short the time is and works adverbially, as in 「一瞬驚いた」.
• Synonym瞬時しゅんじWrittenWritten/formal prose, mostly in 「瞬時に」 to mean instantly, as in 「瞬時に判断する」; 「一瞬」 is also common in speech.
• Synonym刹那せつなWrittenA Buddhist term extended to an extremely short instant; literary, as in 「刹那的」; 「一瞬」 is more general-purpose.
• Synonym一瞬間いっしゅんかんNeutralAn emphatic variant of 「一瞬」, used less often; in everyday speech just say 「一瞬」.
• Synonym瞬く間またたくまNeutralA set phrase for the blink of an eye, mostly in 「瞬く間に」 for how fast something happens; 「一瞬」 also stands alone as a noun.
• RelatedとっさNeutralThe instant before you can think, mostly as 「咄嗟に」 for instinctive reactions; 「一瞬」 only says the time is short.
• Related瞬く間にまたたくまにNeutralAn adverb for something done or happening in a flash, as in 「瞬く間に広まる」「瞬く間に食べ終えた」; 「一瞬」 is broader.
• Related一瞬にしていっしゅんにしてWrittenAn adverbial phrase stressing that something happens or is done in an instant, as in 「一瞬にして消えた」; slightly more written than 「一瞬で」.
• Related須臾しゅゆWrittenAn archaic literary word for a brief moment, also a name for an extremely small number; in modern speech say 「一瞬」 or 「少しの間」.
• Related転瞬てんしゅんWrittenWritten/formal prose for the blink of an eye; very rare. In daily use say 「一瞬」 or 「瞬く間」.
• Antonym永遠えいえんNeutralOpposite of 「一瞬」 in duration: endless, everlasting time.
• Antonym長時間ちょうじかんNeutralA relatively long stretch of time, as in 「長時間労働」; the opposite of 「一瞬」 in duration.
• Antonym永久とわWrittenOpposite of 「一瞬」 in duration: permanence; an elegant word found in lyrics and poetry.

Use 「一瞬」 for a very short moment in everyday speech. Use 「瞬間」 for the moment something happens, 「瞬く間に」 for something done in a flash, and 「咄嗟に」 for an instinctive reaction. 「瞬時」 and 「刹那」 suit written prose. Antonyms: 「永遠」, 「永久」, 「長時間」.

Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only

1. 一度いちど瞬まばたきをするほどの、ごくわずかな時間じかん。副詞ふくし的てきにも用もちいる。
2. ごくわずかな時間じかんで。
3. 少少しょうしょう。少すこしだけ。