1）ahead of （在空间或时间上）超前
如：
Let's cut through the woods and get 【ahead of】 them.加sb
咱们穿过树林抄近路赶到他们前面去.
He had to work hard to remain 【ahead of his classmates】.
他必须努力学习以保持他在同学中的领先地位.
2）in advance 预先,提前 【相当于一个副词,修饰动词】
如：
If there is any change about the time of the meeting,please notify us【 in advance】.修饰notify
开会时间如有变,请提前告诉我们.
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