diffuse nebula vs gaseous nebula

diffuse nebula and gaseous nebula both are nouns.

Word	Noun	Adjective	Verb	Adverb
diffuse nebula	Yes	No	No	No
gaseous nebula	Yes	No	No	No

As nouns, diffuse nebula and gaseous nebula are synonyms defined as:

diffuse nebula and gaseous nebula: a cluster of stars within an intricate cloud of gas and dust

diffuse nebula (noun)	gaseous nebula (noun)
a cluster of stars within an intricate cloud of gas and dust	a cluster of stars within an intricate cloud of gas and dust