precursor

n. 先驱者, 前导, 前兆
【化】 前体; 前身; 产物母体
【医】 先质, 前体(产物母体)

pre.cur.sor

n.（名词）
One that precedes and indicates, suggests, or announces someone or something to come:
先兆：先于并暗示、表明或宣告某人或某事到来的人或事：
例句：
Opposition by colonists to unfair taxation by the British was a precursor of the Revolution.
殖民地居民对英国不公正税收的反抗预示着革命的到来

One that precedes another; a forerunner or predecessor:
前任：先于另一人的人；先锋或先行者：
例句：
Her precursor as school principal was an eminent educator.
她任校长前是一位卓越的教育家

A biochemical substance, such as an intermediate compound in a chain of enzymatic reactions, that gives rise to a more stable or definitive product:
前体：生化物质，如一连串酶反应中的中间化合物，可形成更稳定或明确的结果：
例句：
a precursor of insulin.
胰岛素前体


来源：
Middle English precursoure
中古英语 precursoure
from Old French precurseur
源自 古法语 precurseur
from Latin praecursor
源自 拉丁语 praecursor
from praecursus [past participle of] praecurrere [to run before]
源自 praecursus [] praecurrere的过去分词 [超前于…]
prae- [pre-]
prae- [前缀，表.先于….]
currere [to run] * see kers-
currere [进行] *参见 kers-