mastoidal vs mastoid

mastoidal and mastoid both are nouns.

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

As adjectives, mastoidal and mastoid are synonyms defined as:

As nouns, mastoidal and mastoid are synonyms defined as:

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

Other synonyms of mastoidal include mastoid bone, mastoid process.

mastoidal (noun)	mastoid (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

mastoidal (adjective)	mastoid (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