xiān qián
先前我和他同过学
xiānqián wǒ hé tā tóngguò xué
Previously, I studied together with him.
我们煤矿的机械化程度比先前高多了。注意“以前”可以用在动词后面表示时间，例如“吃饭以前要洗手”，“先前”不能这样用。
wǒmen méikuàng de jīxièhuà chéngdù bǐ xiānqián gāo duō le. zhùyì "yǐqián" kěyǐ yòng zài dòngcí hòumiàn biǎoshì shíjiān, lìrú "chīfàn yǐqián yào xǐshǒu", "xiānqián" bù néng zhèyàng yòng.
The mechanization level of our coal mine is much higher than before. Note that "yǐqián" (before) can be used after verbs to indicate time, for example "wash hands before eating", but "xiānqián" cannot be used this way.