The Sanskrit word guṇa has the basic meaning of "string" or "a single thread or strand of a cord or twine". In more abstract uses, it may mean "a subdivision, species, kind", and generally "quality".
In Samkhya philosophy there are three guṇas (based upon the three "tendencies"), tamas guṇa, sattva guṇa, and rajas guṇa.
ether, associated with the guṇaśábda ("sound") and with the ear.
air, associated with the guṇasparśa ("feeling") and with the skin.
fire, associated with the guṇarūpa ("appearance", and thus color and tangibility) and with the eye.
water, associated with the guṇarasa ("taste", and thus also flavor and tangibility, as well as shape) and with the tongue.
earth, associated with all the preceding guṇas as well as the guṇagandha ("smell") and with the nose.
In Samkhya philosophy
In Samkhya philosophy a guṇa is one of three "tendencies": tamas, sattva, and rajas. These categories have become a common means of categorizing behavior and natural phenomena in Hindu philosophy, and also in Ayurvedic medicine, as a system to assess conditions and diets. Guṇa is the tendency of the mind and not the state of mind or action itself. For instance, sattva guṇa is that force which tends to bring the mind to purity but is not purity itself. Similarly rajas guṇa is that force which tends to bring the mind to perform some action but is not action itself.
Sattva (originally "being, existence, entity") has been translated to mean balance, order, or purity. This typically implies that a person with more of Sattva has a positive or even orderly state of mind. Such a person is psychologically kind, calm, alert, and thoughtful. Compare also the bodhisattvas in Buddhism. IndologistGeorg Feuerstein translates sattva as "lucidity".
Rajas (originally "atmosphere, air, firmament") leads one to activity. This type of activity is explained by the term Yogakshem. Yogakshem is composed of two words: Yoga and Kshem. Yoga in the present context is acquiring something that one does not have. Kshem means losing something that one already has. Rajas is the force that creates desires for acquiring new things and fears for losing something that one has. These desires and fears lead one to activity. (Rajas is etymologically unrelated to the word raja.) Feuerstein translates rajas as "dynamism".
Tamas (originally "darkness", "obscurity") has been translated to mean "too inactive", negative, lethargic, dull, or slow. Usually it is associated with darkness, delusion, or ignorance. A tamas quality also can imply that a person has a self-destructive or entropic state of mind. That person is constantly pursuing destructive activities. Feuerstein translates tamas as "inertia".
In Nyaya philosophy
In Nyaya philosophy, 24 guṇas are enumerated as properties or characteristics of all created things, including śábda, sparśa, rūpa, rasa, and gandha.