hiatus vs foramen

hiatus and foramen both are nouns.

Word	Noun	Adjective	Verb	Adverb
hiatus	Yes	No	No	No
foramen	Yes	No	No	No

As nouns, hiatus and foramen are synonyms defined as:

hiatus and foramen: a natural opening or perforation through a bone or a membranous structure

hiatus (noun)	foramen (noun)
a natural opening or perforation through a bone or a membranous structure	a natural opening or perforation through a bone or a membranous structure
a missing piece (as a gap in a manuscript)
an interruption in the intensity or amount of something