ナイトガウン

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Meanings

1

A loose dress-like garment worn for sleeping, typically by women. The Japanese loanword ナイトガウン is used similarly to the English 'nightgown'.

パジャマ
パジャマ refers to pajamas (a two-piece set), while ナイトガウン is a one-piece nightgown.
寝ね間ま着き
寝間着 is a general native Japanese term for sleepwear, including both nightgowns and pajamas.

Loanword from English 'nightgown'.