1. a substance from which another substance is formed (especially by a metabolic reaction)

2. a person who goes before or announces the coming of another

3. something that precedes and indicates the approach of something or someone

1.先驱；先锋；前身
Aprecursor of something is a similar thing that happened or existed before it, often something which led to the existence or development of that thing.

e.g. Real tennis, an ancientprecursor of the modern game, originated in the eleventh century...
室内网球，现代网球运动的古老前身，起源于11世纪。
e.g. He said that the deal should not be seen as aprecursor to a merger.
他说该笔交易不应该被看作是合并的前兆。

1. 先驱：恶意软件事件表征有两种:恶意软件先驱(precursor)和迹象 (indication),所谓先驱是指恶意软件攻击可能会在将来出现. 迹象是指是指已经出现或是正在出现的表征. 确认感染系统的实体地址的难处有几个因素. 在一个管理良好的网络环境中,

2. 前体物：一般都用mRNA上3个连续核苷序列表示某一野生型菌株因发生基因突变而丧失合成一种或几种生长因子(碱基或氨基酸)的能力,只有从周围环境或培养基中获得这些营养或其前体物(precursor)才能正常生长繁殖的变异类型,称为营养缺陷型.

3. 前驱物：已有研究显 已有研究显 已有研究显 已有研究显 示心房早期收缩是心房颤动之前驱物 (precursor) 示心房早期收缩是心房颤动之前驱物 (precursor) 示心房早期收缩是心房颤动之前驱物 (precursor) 示心房早期收缩是心房颤动之前驱物