一刻|いっこくikkoku[4]odaka (tail-high)

1. nouna moment; a minute; an instant
   一刻いっこくの猶予ゆうよも許ゆるされなかった。↗

   Not a moment could be lost.
2. na-adjectivestubborn; obstinatealso written as 一国, 一克, 一剋

• Synonymつかの間つかのまNeutralA fleeting moment, often tinged with emotion, as in 「つかの間の休息」; 「一刻」 itself simply denotes a very short span of time.
• SynonymひとときNeutralA while or stretch of time, as in 「楽しいひと時」「つらいひと時」; can also refer to a period in the past. 「一刻」 covers only very short spans.
• Synonym寸時すんじWrittenWritten style: a moment, an instant, as in 「寸時も休まず」. Rarer than 「一刻」; in daily speech say 「少しの間」.
• Synonym寸秒すんびょうWrittenWritten style for an extremely short time; even rarer than 「一刻」. In everyday speech use 「一瞬」.
• Synonym分秒ふんびょうNeutralMostly seen in 「分秒を争う」, which is close in meaning to 「一刻を争う」; the two can be swapped freely.
• Synonym寸刻すんこくWrittenWritten style for an instant, as in 「寸刻を惜しむ」. Rarer than 「一刻」 and seldom used in everyday speech.
• Related短時間たんじかんNeutralFor objectively short durations; also works adverbially, as in 「短時間で済む」. 「一刻」 mostly shows up in set phrases like 「一刻も」.
• Antonym永遠えいえんNeutralEternity, something unchanging, as in 「永遠の愛」. The opposite of momentary 「一刻」 in terms of time span.
• Antonym長久ちょうきゅうWrittenWritten style for lasting long, as in 「武運長久」. Opposite of momentary 「一刻」, and rare in everyday use.
• Antonym永久とわWrittenRead とわ: a poetic word for everlastingness, found mostly in lyrics and verse. The opposite of momentary 「一刻」.

For a moment or instant, use 「一刻」, as in 「一刻も早く」「一刻を争う」. A fleeting, wistful moment is 「つかの間」; a stretch of time is 「ひと時」; an objectively short duration is 「短時間」. 「分秒を争う」 swaps with 「一刻を争う」. The 寸- words are rare written terms. The opposite is 「永遠」.

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

1. 僅わずかな時間じかん
2. 一時いちじの四よん分ぶんの一いちの時間じかん。約やく30分ふん。
3. 頑固がんこであること。一国いっこく。一徹いってつ。