The professor wore his academic gown while giving a speech at the graduation ceremony.

gown 是名词，指"长袍、礼服"，特指在正式场合穿着的宽松长外衣。 academic gown 指大学师生在毕业典礼等正式学术场合穿着的长袍，通常有特定颜色和款式来代表不同学位或学校。