たちまち (tachimachi): In an instant; very soon
～たちまち (tachimachi)
Meaning
In an instant; very soon
Formation and usage
たちまち + clause
Notation: N = noun; V dictionary = dictionary-form verb; V stem = the stem before ます; plain clause = plain-form clause; negative stem = the form before ない. Follow the attachment shown above.
Explanation
Emphasizes a rapid change, often one that seems sudden or unexpected.
Examples
会議が終わると、会場はたちまち静かになった。
Once the meeting ended, the venue became quiet in an instant.
試験が終わると、会場はたちまち静かになった。
Once the exam ended, the venue became quiet in an instant.
研修が終わると、会場はたちまち静かになった。
Once the training session ended, the venue became quiet in an instant.
発表会が終わると、会場はたちまち静かになった。
Once the presentation event ended, the venue became quiet in an instant.
面接が終わると、会場はたちまち静かになった。
Once the interview ended, the venue became quiet in an instant.
How related patterns differ
さらに adds or increases; 何といっても singles out the strongest feature, while 何しろ gives a salient reason. さすがに can meet expectations or acknowledge a limit. いったい intensifies a question, 万一 anticipates a risk, and たちまち marks rapid change.