within

注意下面四句里都用of而不用from：

• I live within an easy walk of the park.
• There is no shop within a mile of his house.
• He returned within an hour of his departure.
• He called on me within an hour of his departure.

within an hour of his departure在第三句里是“在他动身以后的一小时以内”，在第四句里是“在他动身以前的一小时以内”。第三句里的of可以改作after。