knowledge base vs knowledge domain

knowledge base and knowledge domain both are nouns.

Word	Noun	Adjective	Verb	Adverb
knowledge base	Yes	No	No	No
knowledge domain	Yes	No	No	No

As nouns, knowledge base and knowledge domain are synonyms defined as:

knowledge base and knowledge domain: the content of a particular field of knowledge

Other synonyms of knowledge base include domain.

knowledge base (noun)	knowledge domain (noun)
the content of a particular field of knowledge	the content of a particular field of knowledge