名词 frequency:

1. the number of occurrences within a given time period

2. the ratio of the number of observations in a statistical category to the total number of observations

3. the number of observations in a given statistical category

FRabbr.故障率（=failure rate）abbr.故障记录（=faillure record）abbr.故障报告（=failure report）Fruja弗鲁娅

1. At some frequencies, it can penetrate walls.
   在一些频率，它能穿透墙壁。
2. Confined waves have definite frequencies.
   被限制的波具有确定的频率。