portal tomb vs cromlech

portal tomb and cromlech both are nouns.

Word	Noun	Adjective	Verb	Adverb
portal tomb	Yes	No	No	No
cromlech	Yes	No	No	No

As nouns, portal tomb and cromlech are synonyms defined as:

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

Other synonyms of portal tomb include dolmen.

portal tomb (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