たちまち・忽ちtachimachi[0]heiban (flat)

1. adverbin an instant; in a moment; immediately; right away; at once
   切符きっぷはたちまち売り切うりきれた。↗

   The tickets were sold out in a moment.
2. adverbsuddenly; all of a sudden; all at once

• SynonymいきなりNeutralStresses no warning at all, catching you off guard, as in 「いきなり殴る」; 「忽ち」 focuses on a change completed in an instant.
• Synonym早速さっそくNeutralUsed for getting started right after news or a decision, as in 「早速試す」 or 「早速苦情が来た」; 「忽ち」 describes a state changing in the blink of an eye.
• Synonymいち早くいちはやくNeutralMeans beating others to it, doing something before anyone else, as in 「いち早く知らせる」; 「忽ち」 is about the blink of an eye.
• SynonymすぐNeutralThe most colloquial word for right away; 「忽ち」 focuses on a state changing in the blink of an eye.
• SynonymすぐさまNeutralStronger than 「すぐ」: at once, without the slightest hesitation; 「忽ち」 centers on a result appearing swiftly.
• SynonymすぐにNeutralEveryday word for right away, common in speech; 「忽ち」 focuses on a change happening in the blink of an eye.
• Synonym直ちにただちにWrittenWritten word typical of directives and announcements, as in 「直ちに避難せよ」; 「忽ち」 describes a change itself.
• Synonym突然とつぜんNeutralStresses the unexpectedness of something happening out of the blue; 「忽ち」 stresses how fast the change is.
• Synonym突如とつじょWrittenWritten word for something occurring suddenly, as in 「突如現れた」; 「忽ち」 stresses speed, not necessarily surprise.
• Synonym早々そうそうNeutralMostly in the pattern 「〜早々」 meaning just after something, as in 「入社早々」; 「忽ち」 does not attach to nouns.
• SynonymさっとNeutralMimetic word for a brisk, swift movement, as in 「さっと立つ」; 「忽ち」 focuses on change happening fast.
• SynonymパッとCasualColloquial mimetic word for happening or vanishing in a flash, as in 「パッと消える」; 「忽ち」 is more written in flavor.
• SynonymにわかにWrittenWritten word for something happening suddenly, as in 「にわかに雨が降る」; 「忽ち」 stresses the speed itself.
• Synonym不意にふいにNeutralCatches you off guard, stressing the unexpected; 「忽ち」 stresses speed and need not imply surprise.
• Synonym急にきゅうにNeutralThe most common spoken word for suddenly or sharply; 「忽ち」 focuses on a change completed in the blink of an eye.
• Synonym即時そくじWrittenWritten word for instant, real-time processing, mostly for systems and transactions, as in 「即時反映」.
• Synonym即刻そっこくWrittenWritten word for immediate action, typical of orders and announcements; 「忽ち」 is used to describe a change.
• Synonym即座にそくざにNeutralFor responding on the spot without delay, as in 「即座に答える」; 「忽ち」 centers on a result appearing swiftly.
• Synonym直にじきにCasualColloquial for soon or before long, as in 「じきに慣れる」; 「忽ち」 is faster and more written in flavor.
• SynonymやにわにWrittenWritten word for acting at once without warning, as in 「やにわに立ち上がる」; 「忽ち」 centers on how quickly the result comes.
• Synonym俄然がぜんWrittenWritten word for a situation or state suddenly turning sharply, as in 「俄然注目を集める」 or 「俄然やる気が出た」; 「忽ち」 stresses the speed of change.
• SynonymたちどころにWrittenWritten word for taking effect on the spot, as in 「たちどころに治る」; close to 「忽ち」 but stresses the here and now.
• RelatedとっさにNeutralFor reacting in a split second or on reflex, as in 「とっさに身をかわす」 or 「とっさに嘘をつく」; 「忽ち」 says a state changes in the blink of an eye.
• Related早々はやばやNeutralMostly in the pattern 「〜早々」 meaning just after something, as in 「入社早々」; 「忽ち」 does not attach to nouns.
• Related迅速じんそくWrittenNa-adjective for swift, prompt action, as in 「迅速な対応」; 「忽ち」 is an adverb.
• Related早くはやくNeutralMeans early or fast, often urging someone on as in 「早く来て」; 「忽ち」 describes a state changing in a blink, whether done or yet to come.
• RelatedさっさとCasualColloquial for doing things briskly, often with an urging or cold tone, as in 「さっさと帰れ」; 「忽ち」 carries no such nuance.
• Related急激きゅうげきNeutralNa-adjective for sharp, drastic change, as in 「急激な変化」; 「忽ち」 is an adverb.
• Antonym徐々にじょじょにNeutralAntonym in pace of change: describes change proceeding gradually, little by little.
• AntonymゆっくりNeutralAntonym in speed: doing something slowly and unhurriedly, the opposite of 「忽ち」.

Use 「忽ち」 when a state changes in the blink of an eye. For simply right away, pick 「すぐ」; for something happening suddenly, 「急に」 or 「突然」; for acting on the spot, 「即座に」; for directives and announcements, 「直ちに」. The opposites are 「徐々に」 and 「ゆっくり」.

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

1. ある状態じょうたいに短時間たんじかんでなる様さま。
2. 急きゅうに起おこる様さま。
3. （方言ほうげん、広島ひろしま）とりあえず。