endopod

This term is a specialized anatomical descriptor used almost exclusively in zoology and invertebrate biology. It describes a specific structural component of biramous limbs, which are limbs that split into two branches. The endopod is the internal branch, contrasting with the exopod, which is the external branch.

Because it refers to a specific biological structure, the word is used in a technical, descriptive register. It is rarely encountered outside of scientific papers, textbooks, or academic discussions regarding arthropod morphology and evolution.