Fetching details from the dictionary...

nightclothes; nightwear; sleepwear; pyjamas; pajamas; nightgown; nightdress
旅館に泊まると浴衣が寝衣として用意される。
When you stay at a ryokan, a yukata is provided as sleepwear.
寝衣のまま朝ごはんを食べることが多い。
I often eat breakfast still in my pajamas.
寒い季節は厚手の寝衣が欠かせない。
A thick pair of pajamas is essential in the cold season.