sea wrack vs seaweed

sea wrack and seaweed both are nouns.

Word	Noun	Adjective	Verb	Adverb
sea wrack	Yes	No	No	No
seaweed	Yes	No	No	No

As nouns, seaweed is a hypernym of sea wrack; that is, seaweed is a word with a broader meaning than sea wrack:

sea wrack: growth of marine vegetation especially of the large forms such as rockweeds and kelp
seaweed: plant growing in the sea, especially marine algae

sea wrack (noun)	seaweed (noun)
growth of marine vegetation especially of the large forms such as rockweeds and kelp	plant growing in the sea, especially marine algae
submerged marine plant with very long narrow leaves found in abundance along North Atlantic coasts