gaseous nebula vs diffuse nebula

gaseous nebula and diffuse nebula both are nouns.

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

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

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

gaseous nebula (noun)	diffuse 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