common vs ordinary

common and ordinary both are nouns.

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

common (noun)	ordinary (noun)
a piece of open land for recreational use in an urban area	(heraldry) any of several conventional figures used on shields
	an early bicycle with a very large front wheel and small back wheel
	a clergyman appointed to prepare condemned prisoners for death
	a judge of a probate court
	the expected or commonplace condition or situation

common (adjective)	ordinary (adjective)
having no special distinction or quality; widely known or commonly encountered; average or ordinary or usual	not exceptional in any way especially in quality or ability or size or degree
belonging to or participated in by a community as a whole; public	lacking special distinction, rank, or status; commonly encountered
commonly encountered
of low or inferior quality or value
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