half-value period

• 半寿命,半衰期

half-value period的用法和样例：

例句

1. The time it takes for half of its original amount to decay is called the half-life.
   衰变至只剩下原来数目一半所需的时间称为该核素的半衰期。
2. It is not necessary to wait until half of a sample has decayed in order to measure the halflife.
   不必一直等到样品衰变一半之后才测量它的半衰期。