The eight possible interactions of a tripartite mimicry system (model, mimic and operator) are defined in terms of positive and negative functions. Five possible states of the system are also recognized in terms of specific composition. From this an eight by five classification matrix is developed, which embraces all normally recognized mimetic situations. Each class is examined for general properties and examples. Special consideration is given to situations (Mullerian mimicry) included here, and to other systems (crypsis, deflective marks) not included, which have been treated differently elsewhere. Mimicry is defined in terms of a tripartite system of living organisms, in which a sensitive signal‐receiver (the operator) misidentifies the mimic as the model. It is emphasized that the system developed here is a classification of mimetic‐interactions, not a classification of species. Discussion is given on some implications of the system in relation to natural selection, and the classification of ecological interactions, convergence and genetic divers