The concept of genre is complex and even controversial, in part due to differences in how genres are conceptualised, modelled and analysed in different disciplines and schools of genre research. The metaphors through which genres are viewed are illustrative: while some talk about genres as species or classes, drawing on biological models, others prefer to think of genres as families or prototypes, and yet others as blueprints or labels. What most approaches have in common, however, is the assumption that genres as forms of semiotic practice are socially based. The concept encourages analysts to look for shared conventions, typification, recurrence and standardisation. This essay reviews three established approaches to genre research within language studies: the Australian-based “Sydney School”, the North American New Rhetoric paradigm and genre research within English for Specific Purposes. It also addresses the issues of classification and stability. It begins however with a brief outline of the historical roots of the concept and particularly the work of Mikhail Bakhtin, which has been instrumental in the emergence of the concept in language studies.