acephalia vs abnormalcy

acephalia and abnormalcy both are nouns.

Word	Noun	Adjective	Verb	Adverb
acephalia	Yes	No	No	No
abnormalcy	Yes	No	No	No

As nouns, abnormalcy is a hypernym of acephalia; that is, abnormalcy is a word with a broader meaning than acephalia:

acephalia: absence of the head (as in the development of some monsters)
abnormalcy: an abnormal physical condition resulting from defective genes or developmental deficiencies

Other hypernyms of acephalia include abnormality.

acephalia (noun)	abnormalcy (noun)
absence of the head (as in the development of some monsters)	an abnormal physical condition resulting from defective genes or developmental deficiencies