convergence: commonness in structures that have evolved independently. For example, the ability to fly is present in many types of animals that do not share a common evolutionary heritage
homology: commonness in structures or genes through evolution of species with a common ancestor. For example, wings in flying mammals, flippers in swimming mammals and forearms in primates are homologous
vestigiality: property of a trait that has been retained throughout evolution but has lost its function – for example, the coccyx (tailbone) in humans