The first collection of aggregates, form or materiality (rūpa-skandha), stands for objects regarded as compounded entities (saṃskṛta). Form is understood to be ‘compounded’ in only one of the two senses in which compoundedness can be interpreted: that of being the product of causes and conditions (the other refers to entities that are produced by putting parts together). The category of form also includes the sensory systems, which from an anatomical and physiological point of view are material forms.

The second collection includes the aggregates of sensation or feeling (vedanā-skandha) and defines the quality of the impressions that result from contact between the sense and its object. Sensations are generally divided into pleasant, unpleasant and neutral and depend on the sensory modality in which they originate. As internal mental states, sensations are both conditioned by, and conditioning of, the habitual tendencies of past karmic activity.

The third collection of aggregates consists of apperception (saṃjña-skandha), and refers to the capacity to comprehend the specific marks (nimitta) of phenomenal objects. The characteristic mark of a phenomenon is its distinctive quality. The term itself is a derivative from saṃ + jñā, meaning ‘to understand,’ ‘to be aware of,’ or more appropriately ‘to make intelligible’ or ‘to cause to be understood,’ thus indicating the causative function of perception predicates. As a synthetic mode of apprehension, apperception is caused by a multiplicity of factors including memories, expectations, dispositions, etc. In this generic sense, apperception might be understood as broadly equivalent to the Aristotelian sensus communis, the faculty that binds together the sensory input into a coherent representation of the object, or to Kant's notion of the transcendental unity of apperception.

The fourth collection of aggregates includes dispositional formations or volitions (saṃskṛta-skandha). Volitions are primarily responsible for bringing forth future states of existence. They include all the conditioned factors that are intrinsic to consciousness (saṃprayuktasaṃskāra) as well as factors that are dissociated from consciousness (viprayuktasaṃskāra). Support for the view that mental factors dissociated from thought are to be included in the category of dispositional formations is found in the Saṃyukta-Nikāya (V, 450): “Delighting in such volitional formations, they generate volitional formations that lead to birth, generate volitional formations that lead to aging, generate volitional formations that lead to death, generate volitional formations that lead to sorrow, lamentation, pain, displeasure, and despair.” Volitions, thus, are habitual latencies that predispose and motivate an individual to have a certain type of experience while at the same time conditioning the response to that experience.

The fifth and last collection contains the aggregates of consciousness (vijñāna-skandha). In contrast to apperception, consciousness is defined as the impression (vijñapti) of each object or as the bare apprehension of each object. Glossing on this definition, later Abhidharma commentators treat consciousness (vijñāna) as referring to an awareness of the object alone (vastumātra) (see Yaśomitra's Vyākhyā ad AK I, 16). Unlike sensation and apperception, which apprehend the specific characteristics of objects, consciousness acts as an integrating and discerning factor of experience.