If you are extremely hungry, you may have a “voracious” appetite (think of the O as an open mouth, ready to devour anything). “Veracious” is an unusual word meaning “truthful, honest” (think about the E in “verify”). A truthful person has “veracity.” “Voracity,” meaning “extreme appetite“ is a rare word you are unlikely to have a use for; “voraciousness” is more common.