Are both words interchangeable? Rikai-chan defines them both as "baby, infant". So what would be the difference?

1 Answer 1


In many contexts they are interchangeable, but strictly speaking 赤ん坊 is the actual word for baby, and 赤ちゃん is like a cute, pet name derived from it.

Also, 赤ん坊 is the spoken (colloquial) form - see sawa's comment for versions that may be more appropriate for formal writing.

  • Perhaps another point is that 赤ちゃん is more common in colloquial and common usage, I think.
    – yadokari
    Commented Jun 12, 2012 at 6:20
  • 4
    赤子 is archaic. You do not use it any more. Formal ways of saying it are 新生児, 乳児, 幼児, or 乳幼児, which cover different ages.
    – user458
    Commented Jun 12, 2012 at 6:26

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