第一(だいいち)

だいいち
noun
first; foremost; number one
number
1. first; number one; the first
The ordinal number meaning first in a sequence or ranking.
第一印象(だいいちいんしょう)が大切(たいせつ)だ。
First impressions are important.
まず第一章(だいいっしょう)から読(よ)み始(はじ)めよう。
Let's start reading from the first chapter.
彼女(かのじょ)はマラソン大会(たいかい)で第一位(だいいちい)を獲得(かくとく)し、家族(かぞく)みんなが喜(よろこ)んだ。
She won first place in the marathon, and her whole family was delighted.
2. foremost; top priority; most important
Used to indicate that something is the most important or should take priority above all else.
安全(あんぜん)第一(だいいち)で作業(さぎょう)してください。
Please work with safety first.
健康(けんこう)が第一(だいいち)だから、無理(むり)をしないでね。
Health comes first, so don't push yourself too hard.
この会社(かいしゃ)は顧客(こきゃく)満足(まんぞく)を第一(だいいち)に考(かんが)え、サービスの改善(かいぜん)に力(ちから)を入(い)れている。
This company puts customer satisfaction first and is committed to improving its services.

第一(だいいち) functions both as an ordinal meaning "the first" in a sequence and as an expression of top priority. In compounds it marks order, while after a noun it conveys that something should come before all else.

Compounds

Pattern: ～第一(だいいち)
Placing 第一(だいいち) after a noun means "X first" or "X is top priority":

Related words

  • 第二(だいに) — second
  • 第三(だいさん) — third
  • 一番(いちばん) — number one; most (more colloquial)

Related Words

Related: 一番(いちばん) (number one)
general
Added 2026.3.25 21:57 · Revised 2026.9.4 21:31
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