There are multiple cross-cutting perspectives on how to organize existing philosophical definitions of biological function. The most common is a definition-based approach. For example, one can group definitions based on whether they treat function as depending only on the way an object is at some point in time or whether that object’s history also matters. While useful at a summary level, this basic typology doesn’t perfectly describe the detailed similarities and differences among definitions, and other cross-cutting typologies have been proposed. A second approach is aims-based and groups definitions in terms of what one can do with them.