The first: 第一 vs 一番 vs 第一番

Question

What are differences among 第一, 一番 and 第一番, all of which seem to mean "the first" in English? Are any of them more suitable for some specific scenarios than the others (e.g. 安全第一 but 世界で一番)?

Answer 1

• 第一番, 第一, 一番: noun 'number one'. 一 still retains its meaning as a number, so it can be replaced by the number character: 第1番, 第1, 1番.

  交響曲第一番/第一/一番/第1番/第1/1番
  'symphony no. 1'

• 第一, 第1 can be used as a prefix.

  第一/第1交響曲
  'symphony no. 1'

• 第一: noun 'has priority'. 一 does not retain the meaning 'one', and cannot be replaced by '1'.

  安全が第一
  'safety is the priority'

• 一番, preferrably written in hiragana as いちばん: adverb 'most'. ー does not retain the meaning 'one', and cannot be replaced by '1'.

  世界でいちばん(高いビル)
  'the {b-/tall-}est (building) in the world'

• 第一, preferrably written in hiragana as だいいち: adverb 'in the first place'. ー does not retain the meaning 'one', and cannot be replaced by '1'.

  だいいち、先生がまだ来ていない
  'the teacher has not come yet in the first place'