cromlech vs portal tomb

cromlech and portal tomb both are nouns.

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

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

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

Other synonyms of cromlech include dolmen.

cromlech (noun)	portal tomb (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