Definition

guṇa m. — a single thread or strand of a cord or twine; string or thread, rope; a garland; a bow-string; the string of a musical instrument, chord; (in geometry) a sinew; ifc. with numerals “fold, times” (as in tri-guṇa, threefold); a multiplier, coefficient (in algebra); subdivision, species, kind; the six subdivisions of action for a king in foreign politics (peace, war, march, halt, stratagem, and recourse to the protection of a mightier king); a secondary element, subordinate or unessential part of any action; a secondary dish (opposed to anna, rice or the chief dish), side-dish; (in grammar) the secondary or less immediate object of an action; a quality, peculiarity, attribute, or property.

An attribute of the five elements: each element has its own peculiar quality or qualities as well as organ of sense — (1) ether has śabda (sound) for its guṇa and the ear for its organ; (2) air has tangibility and sound, the skin; (3) fire has shape or colour, tangibility, and sound, the eye; (4) water has flavour, shape, tangibility, and sound, the tongue; (5) earth has all the preceding guṇas with the addition of its own peculiar guṇa of smell, and the nose for its organ.

In Sāṁkhya philosophy: an ingredient or constituent of Prakṛti, chief quality of all existing beings — namely sattva, rajas, and tamas (goodness, passion, and darkness; or virtue, foulness, and ignorance). Hence also the number “three.”

In Nyāya philosophy twenty-four guṇas are enumerated: (1) rūpa (shape, colour); (2) rasa (savour); (3) gandha (odour); (4) sparśa (tangibility); (5) saṃkhyā (number); (6) parimāṇa (dimension); (7) pṛthaktva (severalty); (8) saṃyoga (conjunction); (9) vibhāga (disjunction); (10) paratva (remoteness); (11) aparatva (proximity); (12) gurutva (weight); (13) dravatva (fluidity); (14) sneha (viscidity); (15) śabda (sound); (16) buddhi or jñāna (understanding or knowledge); (17) sukha (pleasure); (18) duḥkha (pain); (19) icchā (desire); (20) dveşa (aversion); (21) prayatna (effort); (22) dharma (merit or virtue); (23) adharma (demerit); (24) saṃskāra (the self-reproductive quality).

Also: good quality, virtue, merit, excellence; the merit of composition (consistency, elegance of expression); the peculiar properties of letters; the first gradation of a vowel.

From the Bhagavad Gītā

sattvaṁ rajas tama iti guṇāḥ prakṛti-sambhavāḥ
nibadhnānti mahābāho dehe dehinam avyayam

The qualities born of material nature — sattva, rajas, and tamas — bind the Imperishable Embodied One (the ātman) in the body, O Arjuna.

— Bhagavad Gītā, 14

It’s important to remember that the three qualities of physical life here on the planet all basically do a negative thing of binding the ātman to the body, as described above.

You have a choice, though, between sattva, rajas, and tamas — the distinctions of which are very important. But ultimately, as the Yoga Sūtras say, one should go beyond even the best of these, sattva:

nistraigunya bhavarjuna

Be without the three guṇas, O Arjuna.

— Bhagavad Gītā, 2.45

See that your disturbing emotions and concepts exist only in relative reality. They do not exist in genuine reality, and ultimately they are self-liberated. See that it is the same for all contradictions and conflicting appearances — they exist only in relative reality; ultimately, their nature is self-liberated equality. So whatever manifests in your life, look directly at the essence of mind in that very moment, and let go and relax in its true nature, unborn, beyond conceptual fabrication, inexpressible.

— Khenpo Tsültrim Gyamtso Rinpoche