Far from being a universally defined notion, aggression is a changing and multifaceted phenomenon encompassing various concepts. There is no consensus as to how different types of aggression should be classified: multiple ways of doing so using a variety of criteria exist in the scientific literature. Some scientists categorise aggressive acts according to how they are expressed, while others prefer to look at motive, function, purpose and objective. Despite the claim of some authors that distinguishing between different types of aggressive acts is not always productive, categorising these according to different purposes and objectives can be very useful, both for developing theory and because such an approach serves forensic practice as well as preventive and therapeutic interventions, as these focus on the propensities and personality of the individual. Furthermore, given that the main functional classifications analysed show a common tendency to dichotomise, it would seem appropriate for their terminology and some of their measurement instruments to be standardised.