The difference between the two ways to say “f - Cchatty

The difference between the two ways to say “first”: xiān 先 and shǒuxiān 首先

To say that somebody does one thing FIRST then does another, xiān 先 is used for “first.” Xiān 先 is used only before VERBS, and never before NOUNS:

I’ll study first, then watch TV.
Wǒ huì xiān niànshū, zài kàn diànshì.
我会先念书，再看电视。

My father says to learn Chinese well first, and only then go to China to travel.
Wǒ fùqin shuō xiān xuéhǎo Hànyǔ, zài dào Zhōngguó qù lǚyóu.
我父亲说先学好汉语，再到中国去旅游。

Shǒuxiān 首先 can be used to set up a sequence of events, too, but it can stand alone, followed by a comma and then the entire sequence, as in:

After I return home, first I do my homework, and then watch TV.
Huíjiā hòu, shǒuxiān, wǒ zuò zuòyè, zài kàn diànshì.
回家后，首先，我做作业，再看电视。

OR:
✔ CC: Huíjiā hòu, wǒ shǒuxiān zuò zuòyè, zài kàn diànshì.
回家后， 我首先做作业，再看电视。
✖ BC: Huíjiā hòu, xiān wǒ zuò zuòyè, zài kàn diànshì.
回家后，先我做作业，再看电视。

Shǒuxiān 首先 is also used to say “first of all” when giving reasons for something or when giving an explanation of something:

First (of all), studying is more important than watching TV.
Shǒuxiān, niànshū bǐ kàn diànshì zhòngyào.
首先,念书比看电视重要。

First (of all), China is not as rich as the U.S.
Shǒuxiān, Zhōngguó méiyǒu Měiguó nàme fùyù.
首先,中国没有美国那么富裕。