| genus cathaya | (n) one species; related to Pseudotsuga and Larix |
| catha | (n) a genus of African evergreen shrubs characterized by thick leaves and white flowers, Syn. genus Catha |
| catharacta | (n) skuas, Syn. genus Catharacta |
| catharanthus | (n) small genus of erect annual or perennial herbs native to Madagascar; widely naturalized in the tropics; formerly included in genus Vinca, Syn. genus Catharanthus |
| cathartes | (n) type genus of the Cathartidae: turkey vultures, Syn. genus Cathartes |