Vaisheshika divides the multiplicity of nature into six categories, the padārthas.
The six padārthas are:
1) dravya (substance, matter);
2) guna (quality, characteristic);
3) karma (activity);
4) sāmānya (universality);
5) vishesha (distinctiveness);
6) samavāya (inherence, concomitance, the relation between a whole and its parts, between substance and quality, between the general and the particular).
The six padārthas are no mere concepts; rather they are real essences (artha) described by the corresponding word (pada). Kanāda presents his system in the Vaisheshika-Sūtra, which consists of ten adhyāyas (chapters).
Source: The Encyclopedia of Eastern Philosophy and Religion: Buddhism, Hinduism, Taoism, Zen. Shambhala Publications, Inc.
Vaisheshika documents
Books on Vaisheshika
External links: Vaisheshika / Vaiśeṣika Sūtra / The Categories or Padārtha