core concepts
What are the three gunas in Hindu philosophy?
What the tradition says
In Hindu thought, the three gunas are sattva, rajas, and tamas. The word guna means a quality or strand. The tradition holds that these three qualities are present in everything in nature, mixed in different amounts. Sattva is linked to calm, clarity, balance, and light. Rajas is linked to energy, motion, drive, and restlessness. Tamas is linked to heaviness, dullness, rest, and inertia. None is seen as standing fully alone. They blend, and the balance between them shifts from moment to moment and from thing to thing.
Where the idea comes from
This idea is worked out in Samkhya, one of the old systems of Hindu thought, where the gunas are part of how nature itself is explained. The Gita also speaks of the three gunas. It describes how they shape a person's temperament, actions, and choices, and how people can lean toward one quality more than the others at different times.
How they shape mood and food
The gunas are often used to describe people and food. A calm, steady mind may be called sattvic. A busy, driven mood may be called rajasic. A sluggish, heavy feeling may be called tamasic. Foods are spoken of the same way. Fresh, simple foods are often called sattvic, sharp or spicy ones rajasic, and stale or very heavy ones tamasic. This is a way of describing qualities within the tradition, not a medical claim about health.
How people use the idea today
Many people today use the three gunas as a simple way to talk about their state of mind or the feel of their day. Teachers of yoga and meditation often mention them. How much weight a person gives the idea varies a lot, from a serious part of their philosophy to a casual way of speaking.