The claims must be drafted in terms of the "technical features of the invention". This means that claims should must not contain any statements relating, for example, to commercial advantages or other non-technical matters, but statements of purpose should be are allowed if they assist in defining the invention.
It is not necessary that every feature should be is expressed in terms of a structural limitation. Functional features may be included provided that a skilled person would have no difficulty in providing some means of performing this function without exercising inventive skill (see F‑IV, 6.5). For the specific case of a functional definition of a pathological condition, see F‑IV, 4.22.
Claims to the use of the invention, in the sense of the technical application thereof, are allowable.