first 有多种词性，其中就有名词，剑桥词典对作名词的first的定义是：the first person or thing to do or be something, or the first person or thing mentioned，例句有： [ + to infinitive ] She was one of the first to arrive.和He is the first (= very willing) to admit that much of his success is due to his good looks ...
first和firstly作副词时完全同义，都可以表示“第一，首先”，都可用作句子副词，此时first也可写作first of all。 例如： First，I would like to thank everyone for coming. 首先，我要感谢各位光临。 Firstly，I would like to thank everyone who has contributed to this success.
