first可以单独用开头吗

first可以单独用开头。

First， I want to thank my parents.

首先 我要感谢我的父母。

First， we need to finish the homework and housework.

首先，我们需要完成作业和家务。

When he graduated from Harvard， he had a first in English.

他在哈佛毕业时，获得了英语一级优等学位。

This is my first visit to New York.

这是我第一次到纽约

first可以单独用开头吗

可以的，写作文时可以用first，second，third，last but not the least，来分层次表达分论点。