Genus Eimeria is a group of parasitic protozoa that infect various animals, including birds, reptiles, and mammals. This group is commonly referred to as coccidia, due to the shape of its oocysts. The term Eimeria comes from the name of the German zoologist Theodor Eimer, who first described the genus in 1870. Synonyms for Eimeria include Isospora, which is often used for coccidia that infect birds, and Cryptosporidium, which causes diarrheal disease in humans and other mammals. Other synonyms include Eimeriidae, Eimeriina, and Coccidia. These terms are commonly used in scientific research and veterinary medicine to describe this important group of parasites.