common ground vs basis

common ground and basis both are nouns.

Word	Noun	Adjective	Verb	Adverb
common ground	Yes	No	No	No
basis	Yes	No	No	No

As nouns, basis is a hypernym of common ground; that is, basis is a word with a broader meaning than common ground:

common ground: a basis agreed to by all parties for reaching a mutual understanding
basis: a relation that provides the foundation for something

Other hypernyms of common ground include footing, ground.

common ground (noun)	basis (noun)
a basis agreed to by all parties for reaching a mutual understanding	the fundamental assumptions from which something is begun or developed or calculated or explained
	a relation that provides the foundation for something
	the most important or necessary part of something