Roman collar vs clerical collar

Roman collar and clerical collar both are nouns.

Word	Noun	Adjective	Verb	Adverb
Roman collar	Yes	No	No	No
clerical collar	Yes	No	No	No

As nouns, Roman collar and clerical collar are synonyms defined as:

Roman collar and clerical collar: a stiff white collar with no opening in the front; a distinctive symbol of the clergy

Other synonyms of Roman collar include dog collar.

Roman collar (noun)	clerical collar (noun)
a stiff white collar with no opening in the front; a distinctive symbol of the clergy	a stiff white collar with no opening in the front; a distinctive symbol of the clergy