dog collar vs Roman collar

dog collar and Roman collar both are nouns.

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

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

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

Other synonyms of dog collar include clerical collar.

dog collar (noun)	Roman collar (noun)
a collar for a dog	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
necklace that fits tightly around a woman's neck