gumwood vs sweet gum

gumwood and sweet gum both are nouns.

Word	Noun	Adjective	Verb	Adverb
gumwood	Yes	No	No	No
sweet gum	Yes	No	No	No

As nouns, sweet gum is a hyponym of gumwood; that is, sweet gum is a word with a more specific, narrower meaning than gumwood:

gumwood: wood or lumber from any of various gum trees especially the sweet gum
sweet gum: reddish-brown wood and lumber from heartwood of the sweet gum tree used to make furniture

Other hyponyms of gumwood include hazelwood, red gum, satin walnut.

gumwood (noun)	sweet gum (noun)
wood or lumber from any of various gum trees especially the sweet gum	a North American tree of the genus Liquidambar having prickly spherical fruit clusters and fragrant sap
	aromatic exudate from the sweet gum tree
	reddish-brown wood and lumber from heartwood of the sweet gum tree used to make furniture