Equus (genus) a female horse. With rare exceptions, these hybrids are sterile and cannot reproduce. A related hybrid, a hinny, is a cross between a male horse and a female donkey. Other hybrids include the zorse, a cross between a zebra and a horse and a zonkey or zedonk, a hybrid of a zebra and a donkey. In areas where Grévy's zebras are sympatric with plains zebras, fertile hybrids do occur. Equines have significant differences in size, though all are characterized by long heads and necks. Their slender legs support their weight on one digit (which evolved from the middle digits). Grévy's
When a white horse is not a horse is it that yellow or black horses are acceptable in one case and unacceptable in the other case? It is clear that acceptable and unacceptable are mutually contrary. Hence, yellow and black horses are the same, one can respond that there are horses, but one cannot respond that there are white horses. Thus, it is evident that white horses are not horses. This dialogue continues with deliberations over colored and colorless horses and whether "white" and "horse" can be separated from "white horse". Other "Gongsun longzi" chapters discuss "Baima"-related concepts of "jian" "hard; hardness" and "bai" "white; whiteness", "ming" "name;