marten vs black cat

marten and black cat both are nouns.

Word	Noun	Adjective	Verb	Adverb
marten	Yes	No	No	No
black cat	Yes	No	No	No

As nouns, black cat is a hyponym of marten; that is, black cat is a word with a more specific, narrower meaning than marten:

marten: agile slender-bodied arboreal mustelids somewhat larger than weasels
black cat: large dark brown North American arboreal carnivorous mammal

marten (noun)	black cat (noun)
agile slender-bodied arboreal mustelids somewhat larger than weasels	large dark brown North American arboreal carnivorous mammal