free radical

free-radical的词性：
n.（名词）

1. An atom or group of atoms having at least one unpaired electron, which makes it highly reactive.
自由基：至少有一个未配对的电子（这使它具有高度的反应性）的原子或原子团

2. An organic compound in which some of the valence electrons are unpaired, occurring as a normal byproduct of oxidation reactions in metabolism.
自由基化合物：其中有一些价电子未配对的一种有机化合物，作为新陈代谢中氧化反应的正常副产物而存在