There are various schools or traditions of Tibetan Buddhism. The four main traditions overlap markedly, such that "about eighty percent or more of the features of the Tibetan schools are the same". Differences include the use of apparently, but not actually, contradictory terminology, opening dedications of texts to different deities and whether phenomena are described from the viewpoint of an unenlightened practitioner or of a Buddha. On questions of philosophy, there has historically been disagreement regarding the nature of Yogacara and Buddha-nature teachings (and whether these are of expedient meaning or ultimate meaning), which still colours the current presentations of "sunyata" (emptiness) and ultimate reality.