first-string vs regular

first-string is not a noun while regular is a noun.

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

first-string (noun)	regular (noun)
	a garment size for persons of average height and weight
	a regular patron
	a dependable follower (especially in party politics)
	a soldier in the regular army

first-string (adjective)	regular (adjective)
being a regular member of a team	in accordance with fixed order or procedure or principle
of members of a team; not substitutes	(of solids) having clear dimensions that can be measured; volume can be determined with a suitable geometric formula
	(used of the military) belonging to or engaged in by legitimate army forces
	not constipated
	relating to a person who does something regularly
	officially full-time
	not deviating from what is normal
	regularly scheduled for fixed times
	conforming to a standard or pattern
	occurring at fixed intervals
	symmetrically arranged
	often used as intensifiers
	in accord with regular practice or procedure