一斉

• Reading: いっせい
• Romaji: issei
• Kanji breakdown: 一 (ichi/is) — one; 斉 (sei) — even, equal, together
• Pronunciation: /is.seː/

Meaning

Simultaneous; all at once; in concert. Describes many things happening at the same time.

A noun and adverb describing multiple entities acting or occurring simultaneously. Used both as a noun modifier (一斉検査, simultaneous inspection) and adverbially with に (一斉に立ち上がる, to stand up all at once). Common in news, instructions, and descriptions of group actions.

Examples

1. 信号が変わると車が一斉に動き出した。 When the light changed, the cars all started moving at once.
2. 一斉テストの結果が来週発表される。 The results of the simultaneous test will be announced next week.
3. 桜の花が一斉に咲き始めた。 The cherry blossoms all began blooming at the same time.

Usage Guide

Context: group actions, news, instructions, events

Tone: neutral

Origin & History

From Sino-Japanese 一 (ichi/is, one) + 斉 (sei, even/equal/together). Literally 'together as one' — all aligned and acting at the same moment.

Cultural Context

Era: Modern

Generation: All ages

Social background: Universal