inferior vs low-grade

inferior is a noun but low-grade is not a noun.

Word	Noun	Adjective	Verb	Adverb
inferior	Yes	Yes	No	No
low-grade	No	Yes	No	No

inferior (noun)	low-grade (noun)
a character or symbol set or printed or written beneath or slightly below and to the side of another character
one of lesser rank or station or quality

inferior (adjective)	low-grade (adjective)
written or printed below and to one side of another character	of inferior quality
of or characteristic of low rank or importance
of low or inferior quality
having an orbit between the sun and the Earth's orbit
lower than a given reference point
falling short of some prescribed norm