早速|さっそくsassoku[0]heiban (flat)

1. adverbat once; immediately; without delay; promptly
   さっそく仕事しごとにとりかかりましょう。↗

   I will set about my task at once.

• SynonymすぐNeutralThe most common everyday word: 'right away' or 'soon', and also physical closeness; 「早速」 is about getting started on something at once.
• SynonymすぐさまNeutralImmediately, straight after; stresses speed more than 「すぐ」 and sounds slightly more written; 「早速」 is about setting to work on something.
• Synonym早々そうそうNeutral'Just after …', as in 「開店早々」, or doing something in a hurry; 「早速」 does not attach to a noun to mark a point in time.
• Synonym直ちにただちにWrittenWritten/formal: at once, without delay, in a solemn tone typical of instructions and announcements; 「早速」 is more everyday.
• SynonymたちまちNeutralA state changes in an instant, as in 「たちまち売り切れる」; it stresses how fast the result comes, not setting out to do something.
• SynonymすぐにNeutralThe same as 「すぐ」 for the temporal 'right away' and common in speech; for nearness in space, though, 「すぐ」 is usual, as in 「すぐそこ」.
• Synonym即刻そっこくFormalFormal: instantly, often in commands, as in 「即刻退去せよ」; 「早速」 carries no commanding tone.
• Synonym至急しきゅうNeutralUrgent, with all speed, as in 「至急連絡ください」; the emphasis is on urgency, which 「早速」 does not imply.
• Synonym即座にそくざにNeutralOn the spot, as in 「即座に答える」; it stresses an immediate in-place reaction, while 「早速」 stresses getting started on a task.
• Synonym即時そくじWrittenWritten: instant, real-time, as in 「即時対応」; typical of systems and institutional rules.
• SynonymさっさとCasualColloquial: briskly, hurry up, often with impatience or urging, as in 「さっさと帰れ」.
• Synonymいち早くいちはやくNeutralBefore anyone else, ahead of others, as in 「いち早く知らせる」; 「早速」 says nothing about beating others to it.
• SynonymたちどころにWrittenWritten: on the spot, at once, as in 「たちどころに解決する」, with a touch of exaggeration; 「早速」 is about taking action oneself.
• Synonym大至急だいしきゅうNeutralEven more pressing than 「至急」 — as fast as possible, often to push for quick action; 「早速」 has no sense of urgency or urging.
• Synonym猶予なくゆうよなくWrittenWritten/formal prose: handle something with no delay; found mainly in official documents. 「早速」 is more conversational and often opens an exchange.
• Synonym即そくNeutralInstantly, at once; also a conjunction meaning 'namely; that is', and it forms compounds such as 「即決」「即答」.
• Synonym時を移さずときをうつさずWrittenWritten: at once, without letting the moment pass; in daily speech say 「すぐ」 or 「早速」.
• Related一も二もなくいちもにもなくNeutralWithout a moment's hesitation, as in agreeing: 「一も二もなく賛成する」; 「早速」 only says the action starts at once, not whether one consents.
• RelatedやにわにWrittenWritten: suddenly, without warning, with a sense of the unexpected; 「早速」 lacks this abrupt feel.
• Antonym後であとでNeutralAntonym: later on, afterwards — the opposite of 「早速」's acting at once.
• Antonym遅くおそくNeutralAntonym: late, slowly — the opposite of 「早速」's promptness.

Use 「早速」 to get right down to doing something, as in 「早速行ってみた」. For everyday 'right away' say 「すぐ」; in formal contexts 「直ちに」 or 「即刻」; for urgency 「至急」; for beating others to it 「いち早く」; for urging someone on 「さっさと」. Others are narrower: 「早々」 'just after …', 「たちまち」 a sudden result, 「即座に」 an on-the-spot reaction, 「大至急」 extreme urgency.

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

1. すぐに。すぐさま。速すみやかに。
2. 速すみやかなこと。また、そのようなさま。