From Hindupedia, the Hindu Encyclopedia

Visesha means attribute/qualifier.

In metaphysics, Visesha means any quality that helps the observer differentiate between two living/nonliving entities. Essential existence of all entities is absolute, undifferentiated and attribute-less. The difference is only apparent, and that difference is caused by the viseshas assumed by the entity in the phenomenal/temporal context.

The worldview that holds that Viseshas comprise phenomenal world, assuming Viseshas is the beginning and dissolution of Viseshas as the culmination of cycle of existence, is Vaiseshika Darsana.

Vaiseshika is also physics, as it deals with the physical viseshas or physical attributes of entities.

The worldview that holds that atman assumes Viseshas in its bound state and in its liberated state it is one with brahman and void of viseshas, is Visistadvaita. (Visista+ advaita = advaita of atman and brahman, while holding viseshas for atman in the unliberated state. This is in contrast with Advaita where atman never has viseshas, only the upadhi (gross/subtle body) has viseshas).

Visista is a derivative of Visesha, used in the sense of "special".

Vishaya and Visesha are related words - meaning matter and attribute respectively. Vishaya is one that has a visesha.

In grammar, Viseshana which means adjective, is called so because it explains guna/visesha of a noun.

Visesha is associated with Nature; temparaments, principles, faculties, and all that constitutes nature is a visesha in the general sense.

Vaiseshika enumerates nine gunas, that emerge because of the association of Purusha with Prakriti. They are buddhi (intellect), sukha (pleasure), dukha (pain/grief), iccha (like), dvesha (dislike), prayatna (effort), dharma (righteousness), adharma (unrighteousness), sanskara (impression of action). Mimamsakas support the same view.

According to Sankhya, sukha (pleasure), dukha (pain/grief) and moha (attraction) are caused by the three gunas Satva, Rajas and Tamas. Yoga darsana holds the same view.