tang vs rockweed

tang and rockweed both are nouns.

Word	Noun	Adjective	Verb	Adverb
tang	Yes	No	No	No
rockweed	Yes	No	No	No

As nouns, rockweed is a hypernym of tang; that is, rockweed is a word with a broader meaning than tang:

tang (noun)	rockweed (noun)
any of various kelps especially of the genus Laminaria	coarse brown seaweed growing on rocks exposed at low tide
any of various coarse seaweeds
brown algae seaweed with serrated edges
a common rockweed used in preparing kelp and as manure
a tart spicy quality
the taste experience when a savoury condiment is taken into the mouth