 The Abhidharma attempts to individuate and determine the unique identity of each dharma yield complex intersecting taxonomies of dharmas organized by multiple criteria or sets of qualities. Abhidharma texts of different schools proposed different dharma taxonomies, enumerating a more or less finite number of dharma categories. It is important to remember, though, that the term dharma signifies both any category that represents a type of occurrence as well as any of its particular tokens or instances. The Theravāda introduced a system of eighty-two dhamma categories, meaning that there are eighty-two possible types of occurrence in the experiential world, not eighty-two occurrences. These are organized into a fourfold categorization. The first three categories include the bare phenomenon of consciousness (citta) that encompasses a single dhamma type and of which the essential characteristic is the cognizing of an object; associated mentality (cetasika) that encompasses fifty-two dhammas; and materiality or physical phenomena (rūpa) that include twenty-eight dhammas that make up all physical occurrences (Abhidh-av 1). All the eighty-one dhamma types in these three broad categories are conditioned (saṅkhata). Conditioned dhammas arise and cease subject to numerous causes and conditions and constitute sentient experience in all realms of the round of rebirth  (saṃsāra).[8]  The eighty-second dhamma that comprises the fourth category is unconditioned (asaṅkhata): it neither arises nor ceases through causal interaction. The single occurrence in this fourth category is nirvana (Pali, nibbāna).