Definitions:
of chief importance; principal

earliest in time or order

not derived from, caused by, or based on anything else; original

(of an organic compound) having its functional group located on a carbon atom which is bonded to no more than one other carbon atom

denoting or relating to organisms that produce organic compounds from simple substances such as water and carbon dioxide, typically by photosynthesis

relating to or denoting the input side of a transformer or other inductive device.

(in the us) a preliminary election to appoint delegates to a party conference or to select the candidates for a principal, especially presidential, election

a primary colour.

the palaeozoic era.

(in the us) run against (the current holder of a political office) in the preliminary election a party uses to select its candidate for the main election