fortitude vs natural virtue

fortitude and natural virtue both are nouns.

Word	Noun	Adjective	Verb	Adverb
fortitude	Yes	No	No	No
natural virtue	Yes	No	No	No

As nouns, natural virtue is a hypernym of fortitude; that is, natural virtue is a word with a broader meaning than fortitude:

fortitude: strength of mind that enables one to endure adversity with courage
natural virtue: (scholasticism) one of the four virtues (prudence, justice, fortitude, and temperance) derived from nature

Other hypernyms of fortitude include braveness, bravery, courage, courageousness.

fortitude (noun)	natural virtue (noun)
strength of mind that enables one to endure adversity with courage	(scholasticism) one of the four virtues (prudence, justice, fortitude, and temperance) derived from nature