いち早く・逸早く・逸速く|いちはやくichihayaku[3]nakadaka (mid-high)

1. adverbpromptly; quickly; without delay
   ねずみはいち早はやく沈しずみそうな船ふねを見捨みすてる。↗

   Rats leave a sinking ship.
2. adverbbefore others; first

• Synonym早速さっそくNeutralFor getting started on something right away, as in 「早速始めよう」. It stresses immediate action, while 「いち早く」 stresses acting before others.
• Synonym早々そうそうNeutralMostly a suffix meaning just after something, as in 「入学早々」, and it can also mean hurriedly. It lacks the sense of beating others to it.
• SynonymすぐNeutralThe most common word for right away or at once; it also covers physical closeness. It does not carry the nuance of acting ahead of others.
• SynonymすぐさまNeutralMeans immediately, slightly more written than 「すぐ」. It only says no time is lost, without any nuance of getting ahead of others.
• Synonym迅速じんそくWrittenA formal written-style na-adjective for quick action, as in 「迅速な対応」. Unlike the adverb 「いち早く」, it describes speed rather than being first.
• SynonymさっさとCasualColloquial, for doing something briskly and without hesitation, sometimes with a cold, brusque feel. It stresses brisk action, not being first.
• Synonym直ちにただちにFormalFormal, typical of instructions and announcements, as in 「直ちに避難してください」. It stresses immediacy, not being first.
• SynonymパッとNeutralDescribes something happening in a flash, as in 「パッと消える」. It focuses on instantaneous change, not on beating others to it.
• SynonymたちまちNeutralMeans in an instant, as in 「たちまち売り切れる」. It describes a sudden change of state, with no nuance of acting before others.
• Synonym早くはやくNeutralThe most basic word for early or fast, as in 「早く起きる」. It says nothing about acting before other people.
• SynonymとっととCasualColloquial and rough, used in commands like 「とっとと帰れ」 to mean hurry up or clear off. Not for polite or formal situations.
• Synonym大至急だいしきゅうNeutralMeans as soon as possible, the sooner the better; mostly for urging things on at work. 「いち早く」 is about acting before others, not urgency.
• SynonymぱっぱとCasualA colloquial mimetic word for handling things quickly and deftly. It stresses brisk, efficient action, not getting ahead of anyone.
• Synonym直様じきさまWrittenAn old-fashioned word for immediately, on the spot; rare today. Say 「すぐに」 in daily speech, and 「いち早く」 for being first.
• SynonymちゃっとCasualMeans swiftly or nimbly, and also a little or somewhat; dated and rarely used now. It has no nuance of acting before others.
• Synonym猶予なくゆうよなくWrittenWritten-style, meaning without delay; not common. It only says there is no postponing, with no sense of getting ahead of others.
• Synonym疾くとくWrittenAn archaic word for swiftly, also meaning long ago; literary or archaizing in flavor. Normally say 「早く」 or 「すぐ」 instead.
• Related至急しきゅうNeutralMeans urgently, for pressing matters, as in 「至急連絡ください」. It stresses how urgent the matter is; 「いち早く」 stresses being first.
• RelatedさっとNeutralFor quick, crisp action, and for wind or rain rising suddenly. It stresses getting things done in one swift motion, not getting ahead of others.
• RelatedみるみるNeutralFor rapid change before one's eyes, as in 「見る見る大きくなる」. It is about fast change, not a person acting ahead of others.
• Related早いとこはやいとこCasualColloquial for quickly or sooner, as in 「早いとこ片付けよう」; mostly used to urge someone along. No nuance of being first.
• RelatedキビキビNeutralFor brisk, crisp movement or speech, as in 「キビキビ働く」. It stresses efficiency and smartness, not who acts first.
• Related一も二もなくいちもにもなくNeutralMeans acting at once, without a moment's hesitation. The point is the lack of hesitation, not getting ahead of anyone else.
• AntonymゆっくりNeutralThe antonym in speed: slowly and unhurriedly, also fully or well. It contrasts with the swiftness of 「いち早く」.
• Antonym遅くおそくNeutralThe antonym: late in time or slow in action, as in 「遅く起きる」 — the opposite of 「いち早く」's quick, first-off action.

Use 「いち早く」 to act quickly before others, as in 「いち早く情報を入手する」. To just start or do something right away, say 「早速」 or 「すぐ」; in announcements and instructions, 「直ちに」. Most alternatives stress speed, urgency, briskness or sudden change without the 'before others' nuance: 「至急」 and 「大至急」 for urgency, 「さっさと」 and 「とっとと」 (colloquial) for brisk or brusque action, 「たちまち」 and 「パッと」 for instant change. The antonyms are 「遅く」 and 「ゆっくり」.

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

1. 素早すばやく、遅おくれなく行おこなうさま。
2. 他ほかの人ひとより先さきに行おこなうさま。