"The three fundamentals of an EICAT assessment are: 1) the protocol used to perform EICAT assessments (EICAT protocol), 2) the data collected and assessed using the EICAT protocol (EICAT data) and 3) the resulting classification of an alien taxon using the data collected with the EICAT protocol (EICAT classification) (Fig. 1). EICAT protocol: The protocol used to classify alien taxa according to the magnitude of their environmental impacts on native species, as described in detail in the Categories and Criteria and Guidelines documents (see also IUCN 2020a, b; Volery et al. 2020). EICAT data: The evidence collected during EICAT assessments and provided as supporting information for EICAT classifications, including all records of impact for the taxon under assessment and their categories and criteria. The type of data and the standardised process in which it is collected is governed by the EICAT protocol. EICAT classification: The classification of any alien taxon (mostly species) according to the EICAT Categories and Criteria and Guidelines (IUCN 2020a, b), i.e. the maximum impact recorded for the taxon and associated mechanism and confidence score."