In biology, functions describe what a trait or process does or how it behaves in the context of natural selection. Functional discussions attempt to explain the reasons behind an organism or process occurring within an organism or ecosystem and are intertwined with 'adaptation', which is one of the functional characteristics of an organism. 

In general, function refers to the operational purpose or result of a mechanism, so we can speak of parallel functions that exist in the natural and human worlds. For example, adhesion occurs in both geckos and man-made products such as medical dressings.