She bought a new night-gown because the old one had been worn for three years.

night-gown 是由 night（夜晚）和 gown（长袍、礼服）组成的复合词，字面意思是"夜间穿的长袍"，指女性睡觉时穿的宽松衣服，即"睡衣"。 gown 本身指正式场合穿的长袍或礼服，在这里特指睡衣。