According to the Vaisheshika school, all things that exist, that can be cognized and named are s (literal meaning: the meaning of a word), the objects of experience. All objects of experience can be classified into six categories, dravya (substance),  (quality), karma (activity),  (generality),  (particularity) and  (inherence). Later s ( and Udayana and ) added one more category abhava (non-existence). The first three categories are defined as artha (which can perceived) and they have real objective existence. The last three categories are defined as  (product of intellectual discrimination) and they are logical categories.
# Dravya (substance): There are nine substances. They are,  (earth), ap (water), tejas (fire),  (air),  (ether),  (time), dik (space),  (self or soul) and manas (mind). The first five are called s, the substances having some specific qualities so that they could be perceived by one or the other external senses.
# Guṇa (quality): The  mentions 17 s (qualities), to which  added another 7. While a substance is capable of existing independently by itself, a  (quality) cannot exist so. The original 17 s (qualities) are,  (colour), rasa (taste), gandha (smell),  (touch),  (number),  (size/dimension/quantity),  (individuality),  (conjunction/accompaniments),  (disjunction),  (priority), aparatva (posteriority), buddhi (knowledge), sukha (pleasure),  (pain),  (desire),  (aversion) and prayatna (effort). To these  added gurutva (heaviness), dravatva (fluidity), sneha (viscosity), dharma (merit), adharma (demerit),  (sound) and  (faculty).
# Karma (activity): The karmas (activities) like s (qualities) have no separate existence, they belong to the substances. But while a quality is a permanent feature of a substance, an activity is a transient one.  (ether),  (time), dik (space) and  (self), though substances, are devoid of karma (activity).
# Sāmānya (generality): Since there are plurality of substances, there will be relations among them. When a property is found common to many substances, it is called .
#  (particularity): By means of , we are able to perceive substances as different from one another. As the ultimate atoms are innumerable so are the s.
#  (inherence):  defined  as the relation between the cause and the effect.   defined it as the relationship existing between the substances that are inseparable, standing to one another in the relation of the container and the contained. The relation of  is not perceivable but only inferable from the inseparable connection of the substances.
# Abhava (non-existence)