直ちに|ただちにtadachini[1]atamadaka (head-high)

1. adverbat once; immediately; right away; without delay
   我々われわれは直ただちにこの問題もんだいに対処たいしょしなければならない。↗

   We should deal with this matter without delay.
2. adverbdirectly (face, lead to, etc.); automatically (mean, result in, etc.)

• SynonymすぐにNeutralThe everyday default for 'right away', at home in both speech and writing; 「直ちに」 is more formal and typical of announcements and instructions.
• Synonym早速さっそくNeutralFor getting started on something right away, as in 「早速試してみる」 or 「早速出発する」; 「直ちに」 stresses that there is no time to lose.
• SynonymすぐCasualColloquial 'right away'; it can also mean very close by or easy, while 「直ちに」 is more formal and can also signal a direct link or consequence.
• SynonymすぐさまWrittenWritten style for acting at once, right on the heels of something; common in narration. 「直ちに」 turns up more in commands and rules.
• Synonym即刻そっこくWrittenWritten, and close to 「直ちに」 but with a more urgent ring; typical of orders, as in 「即刻退去せよ」.
• Synonym即座にそくざにNeutralFor answering or reacting on the spot, as in 「即座に答える」; 「直ちに」 stresses simply not putting things off.
• Synonym早々そうそうNeutralMostly a suffix, as in 「開店早々」, and can also mean doing things in haste; 「直ちに」 simply means immediately.
• Synonymいち早くいちはやくNeutralHighlights beating others to it, moving faster than anyone else; 「直ちに」 stresses no delay.
• Synonym即時そくじWrittenWritten; works as noun and adverb for immediate, real-time handling, as in 「即時払い」 or 「即時対応」; leans business and technical.
• SynonymさっさとCasualColloquial for getting things done briskly and without dithering, often as a nudge like 「さっさとしろ」; 「直ちに」 is more formal.
• SynonymたちまちNeutralFor a state being reached in an instant, as in 「たちまち売り切れる」; 「直ちに」 centers on taking action.
• SynonymとっさにNeutralFor split-second reactions with no time to think; 「直ちに」 usually means urgent action and can also say a result follows directly.
• SynonymすかさずNeutralFor jumping in at once, without hesitation, as in 「すかさず反論する」; 「直ちに」 is more formal.
• SynonymたちどころにWrittenWritten; for something happening on the spot, all at once, often an effect, as in 「たちどころに治る」.
• Synonym時を移さずときをうつさずWrittenA written idiom for acting without a moment's delay; in everyday speech you would say 「すぐに」.
• Related一気にいっきにNeutralFor finishing something in one go, without a break; 「直ちに」 is about starting without delay.
• RelatedやにわにWrittenWritten; for acting on the spot, out of the blue; 「直ちに」 carries no sense of suddenness.
• Related直様じきさまWrittenAn old-fashioned way of saying 'at once'; today you would say 「すぐに」.
• Antonym後であとでNeutralThe temporal opposite of 「直ちに」: a while later, afterwards.
• Antonym遅れてNeutralThe temporal opposite of 「直ちに」: falling behind or arriving a step late.

For everyday 'right away', 「すぐに」 is the natural choice. Use 「直ちに」 in announcements, rules and instructions, or for a direct link between things. 「即刻」 fits urgent written orders, 「即座に」 on-the-spot reactions, 「早速」 getting started on something, and 「たちまち」 changes that happen in an instant. The rest are narrower: 「いち早く」 beating others to it, 「一気に」 in one go, 「さっさと」 briskly, 「すかさず」 jumping straight in, and 「即時」 in business or technical set phrases.

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

1. 間あいだをおかず行動こうどうするさま。
2. じかに結むすびついておりすぐに判断はんだんされるさま。