In zoological anatomy, a cloaca is the posterior opening that serves as the only such opening for the intestinal, urinary, and genital tractss of certain animal species. All birds, reptiles, and amphibians possess this orifice, by which they simultaneously evacuate both urine and feces. In contrast, each individual among most species of placental mammals and bony fishes has, in lieu of a cloaca, a specialized opening for at least one of these tracts.
"Cloaca" is Latin for "sewer"; it may also be used (but not commonly) with that meaning in English.
