母语
Mother language
第二外语
The second language
中文语境：
我的母语是中文和台语。
我的第一个外语是英文。
我的第二个外语是西班牙语。
我的第三个外语是日语。
英文语境：
My mother language is Chinese and Taiwanese.
My second language is English.
My second language is Spanish.
My second language is Janpanese.

我的第一个外语是俄罗斯语My second language is Russian.

What is your first foreign language?