mastoid vs mastoidal

mastoid and mastoidal both are nouns.

Word	Noun	Adjective	Verb	Adverb
mastoid	Yes	Yes	No	No
mastoidal	Yes	Yes	No	No

As adjectives, mastoid and mastoidal are synonyms defined as:

As nouns, mastoid and mastoidal are synonyms defined as:

mastoid and mastoidal: process of the temporal bone behind the ear at the base of the skull

Other synonyms of mastoid include mastoid bone, mastoid process.

mastoid (noun)	mastoidal (noun)
process of the temporal bone behind the ear at the base of the skull	process of the temporal bone behind the ear at the base of the skull

mastoid (adjective)	mastoidal (adjective)
relating to or resembling a nipple	relating to or resembling a nipple
of or relating to or in the region of the mastoid process