wood coal vs brown coal

wood coal and brown coal both are nouns.

Word	Noun	Adjective	Verb	Adverb
wood coal	Yes	No	No	No
brown coal	Yes	No	No	No

As nouns, wood coal and brown coal are synonyms defined as:

Other synonyms of wood coal include lignite.

wood coal (noun)	brown coal (noun)
intermediate between peat and bituminous coal	intermediate between peat and bituminous coal
a carbonaceous material obtained by heating wood or other organic matter in the absence of air