homologous structures

Homologous structures are body parts that are alike because the species share a common ancestor.  Unlike analogous structures, meaning that it preforms the same function, homologous structures don't necessarily preform the same function; they just share a common ancestral origin. As an example, I have a bird's wing, which is homologous to the human arm. They have the same basic skeletal structure, and are derived from the same origin, but they are used differently.