common vs informal

common is a noun but informal is not a noun.

Word	Noun	Adjective	Verb	Adverb
common	Yes	Yes	No	No
informal	No	Yes	No	No

common (noun)	informal (noun)
a piece of open land for recreational use in an urban area

common (adjective)	informal (adjective)
having no special distinction or quality; widely known or commonly encountered; average or ordinary or usual	not formal
belonging to or participated in by a community as a whole; public	used of spoken and written language
commonly encountered	having or fostering a warm or friendly and informal atmosphere
of low or inferior quality or value	not officially recognized or controlled
being or characteristic of or appropriate to everyday language
of or associated with the great masses of people
to be expected; standard
common to or shared by two or more parties
lacking refinement or cultivation or taste