approximately

almost, nearly, about, approximately, around, roughly

这些副词均有“大约，差不多”之意。
almost: 指在程度上相差很小，差不多。
nearly: 与almost含义基本相同，侧重指数量、时间或空间上的接近。
about: 常可分almost和nearly换用，但about用于表示时间、数量的“大约”时，实际数量可能多也可能少。
approximately: 多用于书面语，指精确度接近某个标准以致误差可忽略不计。
around: 多用于非正式场合，常见于美国英语。
roughly: 指按粗略估计，常代替about。

副词 approximately:

1. (of quantities) imprecise but fairly close to correct
   同义词：about, close to, just about, some, roughly, more or less, around, or so

1. Approximately has400 pages when this book is completed.
   当这本书完成时大约有四百页。
2. A unit of time corresponding approximately to one cycle of the moon's phases, or about30 days or4 weeks.
   月大约和月亮盈亏的一个周期相当的时间单位，或约三十天或四周
3. At a time near to; at approximately
   将近。。。的时候; 大约在。。。
4. The plane will be taking off in approximately five minutes.
   飞机大约五分钟后就起飞。