char vs Arctic char

char and Arctic char both are nouns.

Word	Noun	Adjective	Verb	Adverb
char	Yes	No	Yes	No
Arctic char	Yes	No	No	No

As nouns, Arctic char is a hyponym of char; that is, Arctic char is a word with a more specific, narrower meaning than char:

char: any of several small trout-like fish of the genus Salvelinus
Arctic char: small trout of northern waters; landlocked populations in Quebec and northern New England

Other hyponyms of char include Salvelinus alpinus.

char (noun)	Arctic char (noun)
any of several small trout-like fish of the genus Salvelinus	small trout of northern waters; landlocked populations in Quebec and northern New England
a human female employed to do housework
a charred substance

char (verb)	Arctic char (verb)
burn slightly and superficially so as to affect color
burn to charcoal