dolmen vs cromlech

dolmen and cromlech both are nouns.

Word	Noun	Adjective	Verb	Adverb
dolmen	Yes	No	No	No
cromlech	Yes	No	No	No

As nouns, dolmen and cromlech are synonyms defined as:

dolmen and cromlech: a prehistoric megalithic tomb typically having two large upright stones and a capstone

Other synonyms of dolmen include portal tomb.

dolmen (noun)	cromlech (noun)
a prehistoric megalithic tomb typically having two large upright stones and a capstone	a prehistoric megalithic tomb typically having two large upright stones and a capstone