first有四個詞形：adj.adv.n.pron.這里主要談adj.和adv.
first adj.序數詞 第一的
Example:He was the first student who arrived at the classroom.
adv.首先
First I fed the baby.Then I made myself a sandwich.
at first是一個介詞短語在句中充當狀語
首先
At first I was nervous,but I soon started to relax.
補充一個firstly 修飾句子的副詞 首先
The plan was not practical,firstly because of the cost,and secondly because local people did not support it.
通?？苫ビ?但有差別,需查詞典體會.