What is the meaning of Precursor?

That which precurses: a forerunner, predecessor, or indicator of approaching events.

One of the compounds that participates in the chemical reaction that produces another compound.

Caused by the following symbol.

precursory, preceding

precursor

precursor, forerunner

precursor; forerunner (something that led to the development of another)

precursory (pertaining to events that will follow)

precursor

precursory, preceding

precursor, forerunner

Source: wiktionary.org