星期 + Number
星期二 (xīngqī'èr) means 'Tuesday' and follows the Chinese system of naming weekdays by number, where 二 means 'two' (the second day of the week). Days of the week in Chinese use 星期 followed by a number from one to six, with Sunday being 星期天 or 星期日.
星期二我有一个很重要的会议。
xīngqī èr wǒ yǒu yī gè hěn zhòngyào de huìyì.
I have a very important meeting on Tuesday.
我们每个星期二一起打篮球。
wǒmen měi gè xīngqī èr yīqǐ dǎ lánqiú.
We play basketball together every Tuesday.
下个星期二是他的生日。
xià gè xīngqī èr shì tā de shēngrì.
Next Tuesday is his birthday.