The word used is in the series is yokai and is basically a blanket term for all kinds of supernatural creatures, monsters, etc. There are certain subsets of yokai which are named after their certain characteristics. Inuyasha himself belongs to the subset of hanyou (half demon) while simultaneously could also be considered an Inugami, or dog demon (Inu means dog), as would be his brother Sesshoumaru. Kouga would be an Okami, while Naraku is a Tsuchigumo (fitting also because Naraku’s name when he was still human was “Onigumo”, which I think would literally mean “ogre spider”.