Dravya is the primary category of existence in Vaisheshika philosophy because it is that which possesses qualities and actions. The other categories, such as Guna, Karma, and Vishesha, are all dependent on Dravya for their existence.

There are nine types of Dravya in Vaisheshika philosophy: Prithvi (earth), Ap (water), Tejas (fire), Vayu (air), Akasha (ether), Kala (time), Dik (space), Atman (soul), and Manas (mind).

Dharma is not a type of Dravya in Vaisheshika philosophy. The nine types of Dravya are Prithvi, Ap, Tejas, Vayu, Akasha, Kala, Dik, Atman, and Manas.

The qualities of Prithvi (earth) in Vaisheshika philosophy are solidity, hardness, and heaviness. These qualities are unique to Prithvi and distinguish it from the other types of Dravya.

Prithvi (earth) is the substance that is responsible for the sense of smell in Vaisheshika philosophy. This is because Prithvi is the only substance that has the quality of solidity, which is necessary for the sense of smell to function.

Velocity is not an action of Dravya in Vaisheshika philosophy. The actions of Dravya are motion, acceleration, and combination.

Samyoga is the process by which two or more Dravyas combine to form a new Dravya called in Vaisheshika philosophy. This process is also known as conjunction or union.

Ap (water) is the substance that is responsible for the sense of taste in Vaisheshika philosophy. This is because Ap is the only substance that has the quality of fluidity, which is necessary for the sense of taste to function.

Solidity is not a quality of Ap (water) in Vaisheshika philosophy. The qualities of Ap are fluidity, coldness, and wetness.

Tejas (fire) is the substance that is responsible for the sense of sight in Vaisheshika philosophy. This is because Tejas is the only substance that has the quality of heat, which is necessary for the sense of sight to function.

Cooling is not an action of Tejas (fire) in Vaisheshika philosophy. The actions of Tejas are burning, heating, and illuminating.

Vayu (air) is the substance that is responsible for the sense of touch in Vaisheshika philosophy. This is because Vayu is the only substance that has the quality of motion, which is necessary for the sense of touch to function.

Solidity is not a quality of Vayu (air) in Vaisheshika philosophy. The qualities of Vayu are motion, velocity, and acceleration.

Akasha (ether) is the substance that is responsible for the sense of hearing in Vaisheshika philosophy. This is because Akasha is the only substance that has the quality of sound, which is necessary for the sense of hearing to function.

Solidity is not a quality of Akasha (ether) in Vaisheshika philosophy. The qualities of Akasha are sound, space, and time.