Under the EPC the claims must define the matter for which protection is sought "in terms of the technical features of the invention" (R. 43(1) EPC). In G 2/88 the Enlarged Board described the technical features of the invention as being the physical features which are essential to it. The technical features of a claim to a physical entity are the physical parameters of the entity, and the technical features of a claim to an activity are the physical steps which define such activity. The Enlarged Board also pointed out, however, that the boards of appeal had in a number of cases allowed the technical features to be defined functionally in certain instances. See in this chapter II.A.3.4.