最中に【さいちゅうに】

最中に (さいちゅうに) means "right in the middle of" or "while (something is happening)". It emphasizes that an action or event is actively in progress at the very moment something else occurs. Compared to more neutral expressions like ま間に or ているとき時に, 最中に stresses that one is at the peak or core of the activity – and the interrupting event is often unexpected, inconvenient, or noteworthy.

Structure

• Verb[ている] + 最中に: The most common pattern. The ている form emphasizes the ongoing nature of the action.

  しょくじ食事をしているさいちゅう最中にでんわ電話がなった鳴った。

  The phone rang right in the middle of my meal.

• Noun + の + 最中に: Used with action nouns.

  かいぎ会議のさいちゅう最中にじしん地震がおきた起きた。

  An earthquake occurred in the middle of the meeting.

• Verb[dictionary form] + 最中に: Sometimes seen, though the ている form is more standard.

Nuance

最中に highlights that you are deeply engaged in the activity when something happens. The second clause typically describes an interruption or unexpected event.

Because of this nuance, 最中に sounds unnatural when the second event is something planned or expected. For example, saying 「勉強している最中に、10時になった」 would sound odd because 10 o'clock arriving is not an unexpected interruption.

最中だ – sentence-ending use

最中 can also appear at the end of a sentence with だ/です to indicate that something is currently in progress right now.

Comparison with 途中（に）

While とちゅう途中 (とちゅう) means "on the way" or "partway through" and can describe being in transit or at some point during a process, 最中に emphasizes being at the height or core of the activity.