char vs bone char

char and bone char both are nouns.

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

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

char: a charred substance
bone char: black substance containing char in the form of carbonized bone; used as a black pigment

Other hyponyms of char include animal black, animal charcoal, bone black, snuff.

char (noun)	bone char (noun)
any of several small trout-like fish of the genus Salvelinus	black substance containing char in the form of carbonized bone; used as a black pigment
a human female employed to do housework
a charred substance

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