1st vs primary

1st is not a noun while primary is a noun.

Word	Noun	Adjective	Verb	Adverb
1st	No	Yes	No	No
primary	Yes	Yes	No	No

1st (noun)	primary (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

1st (adjective)	primary (adjective)
preceding all others in time or space or degree	of first rank or importance or value; direct and immediate rather than secondary
	of or being the essential or basic part
	most important element
	not derived from or reducible to something else; basic