primary vs first-string

primary is a noun but first-string is not a noun.

Word	Noun	Adjective	Verb	Adverb
primary	Yes	Yes	No	No
first-string	No	Yes	No	No

primary (noun)	first-string (noun)
a preliminary election where delegates or nominees are chosen
one of the main flight feathers projecting along the outer edge of a bird's wing
coil forming the part of an electrical circuit such that changing current in it induces a current in a neighboring circuit
(astronomy) a celestial body (especially a star) relative to other objects in orbit around it

primary (adjective)	first-string (adjective)
of first rank or importance or value; direct and immediate rather than secondary	being a regular member of a team
of or being the essential or basic part	of members of a team; not substitutes
most important element
not derived from or reducible to something else; basic