Precursor (chemistry)
WordNet
noun
(1) An indication of the approach of something or someone
(2) A person who goes before or announces the coming of another
(3) A substance from which another substance is formed (especially by a metabolic reaction)
WiktionaryText
Noun
- That which precurses, a forerunner, a predecessor, an indicator of approaching events.
- One of the compounds that participates in the chemical reaction that produces another compound.