Etic distinctions are explained in terms of various etic frameworks or classificatory grids. Classic examples of etic frameworks include: †Linnaean taxonomy; disease, in medical science; and the genealogical grid. Linnaean taxonomy is intended as a universal, hierarchical system for the classification of plants and animals on the basis of relative differences and similarities, and it entails an implicit theory of evolutionary relatedness. In contrast, the non-Linnaean classification of plants and animals in different cultures (e.g., the classification of bats as ‘birds’ rather than as ‘mammals’) is based on emic criteria, which may be quite different. Medical anthropologists make a similar distinction between ‘disease’ (a pathological condition, as defined by medical science) and ‘illness’ (the culturally-specific understanding of disease). Diseases are defined in the same way wherever Western †biomedicine is practised, whereas what counts as a particular illness varies in different cultural contexts.