punishable vs penal

punishable and penal both are adjectives.

Word	Noun	Adjective	Verb	Adverb
punishable	No	Yes	No	No
penal	No	Yes	No	No

As adjectives, punishable and penal are synonyms defined as:

punishable and penal: (of an act or offense) subject to punishment by law

punishable (adjective)	penal (adjective)
liable to or deserving punishment	of or relating to punishment
(of an act or offense) subject to punishment by law	(of an act or offense) subject to punishment by law
	serving as or designed to impose punishment