Black Friar vs friar preacher

Black Friar and friar preacher both are nouns.

Word	Noun	Adjective	Verb	Adverb
Black Friar	Yes	No	No	No
friar preacher	Yes	No	No	No

As nouns, Black Friar and friar preacher are synonyms defined as:

Black Friar and friar preacher: a Roman Catholic friar wearing the black mantle of the Dominican order

Other synonyms of Black Friar include Blackfriar, Dominican.

Black Friar (noun)	friar preacher (noun)
a Roman Catholic friar wearing the black mantle of the Dominican order	a Roman Catholic friar wearing the black mantle of the Dominican order