domain vs knowledge base

domain and knowledge base both are nouns.

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

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

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

Other synonyms of domain include knowledge domain.

domain (noun)	knowledge base (noun)
the content of a particular field of knowledge	the content of a particular field of knowledge
people in general; especially a distinctive group of people with some shared interest
(mathematics) the set of values of the independent variable for which a function is defined
territory over which rule or control is exercised
a particular environment or walk of life