1.
firstly; first of all; in the first place
Used to introduce the first point in a series of arguments or reasons. Also used to emphasize that something is the most important consideration.
第一に、安全を確認してください。
First of all, please confirm safety.
第一に健康、第二に家族が大切だ。
Health comes first, family comes second.
この計画には問題がある。第一に予算が足りない。
There are problems with this plan. First of all, the budget is insufficient.
第一に introduces the first and often most important point in a series. It is used in logical arguments, speeches, and essays.
SERIES PATTERN:
Often used with sequential markers:
- 第一に (firstly)
- 第二に (secondly)
- 第三に (thirdly)
WITHOUT に:
第一 alone (without に) emphasizes priority: 健康第一 (health first), 安全第一 (safety first).
SIMILAR WORDS:
- まず: first, to begin with (more colloquial and versatile)
- 最初に: at first, initially (temporal focus)
- 何よりも: above all else (strongest emphasis on priority)
- そもそも: in the first place (challenges premises, more confrontational)
REGISTER:
Neutral to formal. Common in structured arguments and formal writing. In casual speech, まず is preferred.