According to the Yogacara school, rūpa is not matter as in the metaphysical substance of materialism. Instead it means both materiality and sensibility—signifying, for example, a tactile object both insofar as that object is made of matter and that the object can be tactically sensed. In fact rūpa is more essentially defined by its amenability to being sensed than its being matter: just like everything else it is defined in terms of its function; what it does, not what it is. As matter, rūpa is traditionally analysed in two ways: as four primary elements (Pali, "mahābhūta"); and, as ten or twenty-four secondary or derived elements.