One who, or that which, precedes an event, and indicates its approach; a forerunner; a harbinger.

A substance, cell, or cellular component from which another substance, cell, or cellular component is formed.

Something that precedes, (for example, Levodopa is a precursor to dopamine in that levodopa is converted to dopamine in the brain).

within a series of chemical and biochemical transformations where one chemical compound leads to another in a synthetic pathway, the precursor is the chemical compound that is necessary for the next chemical compound in the pathway to be synthesized.

Either the PAN or pitch fibers from which carbon and graphite fibers are derived.

The PAN, rayon or pitch fibers from which carbon or graphite fibers are derived.

For carbon fibers, the rayon, PAN, or pitch fibers from which carbon fibers are made.