一 斉(いっせい)に

いっせいに

adverb

all at once; simultaneously; in unison

time-general

1. all at once; simultaneously; in unison

Describes multiple people or things acting at the same time in a coordinated or synchronized manner.

生徒(せいと)たちが一斉(いっせい)に立(た)ち上(あ)がった。

The students all stood up at once.

合図(あいず)とともに一斉(いっせい)にスタートした。

They all started simultaneously at the signal.

桜(さくら)の花(はな)が一斉(いっせい)に咲(さ)き始(はじ)めると、公園(こうえん)は大勢(おおぜい)の花見客(はなみきゃく)でにぎわう。

When the cherry blossoms all start blooming at once, the park bustles with crowds of flower-viewing visitors.

Usage

一斉(いっせい)に emphasizes that an action happens simultaneously across a group. The noun form 一斉(いっせい) can also be used as a prefix: 一斉(いっせい)検査(けんさ) (simultaneous inspection), 一斉(いっせい)送信(そうしん) (mass sending/broadcast).
Compared to 同時(どうじ)に, which simply means "at the same time," 一斉(いっせい)に implies a larger group acting together and often carries a more dramatic or striking impression.

Common collocations

一斉(いっせい)に立(た)ち上(あ)がる (to stand up all at once)
一斉(いっせい)に始(はじ)まる (to begin simultaneously)
一斉(いっせい)に咲(さ)く (to bloom all at once)
一斉(いっせい)検挙(けんきょ) (mass arrest)

Related Words

Compare: 同時(どうじ) (at the same time)

Compare: 軒並(のきな)み (across the board)

Compare: 同時(どうじ)に (at the same time)

general

Added 2026.3.9 17:30 · Revised 2026.9.2 13:01

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