Blackfriar vs Black Friar

Blackfriar and Black Friar both are nouns.

Word	Noun	Adjective	Verb	Adverb
Blackfriar	Yes	No	No	No
Black Friar	Yes	No	No	No

As nouns, Blackfriar and Black Friar are synonyms defined as:

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

Other synonyms of Blackfriar include Dominican, friar preacher.

Blackfriar (noun)	Black Friar (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