tang vs kelp

tang and kelp both are nouns.

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

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

tang (noun)	kelp (noun)
any of various kelps especially of the genus Laminaria	large brown seaweeds having fluted leathery fronds
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