vii vs seven

vii is not a noun while seven is a noun.

Word	Noun	Adjective	Verb	Adverb
vii	No	Yes	No	No
seven	Yes	Yes	No	No

As adjectives, vii and seven are synonyms defined as:

Other synonyms of vii include 7.

vii (noun)	seven (noun)
	one of four playing cards in a deck with seven pips on the face
	the cardinal number that is the sum of six and one

vii (adjective)	seven (adjective)
being one more than six	being one more than six