Ptolemy vs Ptolemaic

Ptolemy is a noun but Ptolemaic is not a noun.

Word	Noun	Adjective	Verb	Adverb
Ptolemy	Yes	No	No	No
Ptolemaic	No	Yes	No	No

Ptolemy (noun)	Ptolemaic (noun)
an ancient dynasty of Macedonian kings who ruled Egypt from 323 BC to 30 BC; founded by Ptolemy I and ended with Cleopatra
Alexandrian astronomer (of the 2nd century) who proposed a geocentric system of astronomy that was undisputed until the late Renaissance

Ptolemy (adjective)	Ptolemaic (adjective)
	of or relating to the astronomer Ptolemy
	of or relating to the geocentric Ptolemaic system