Buddhi (Sanskrit: बुद्धि) is derived from the Vedic Sanskrit root Budh (बुध् ), which literally means "to wake, be awake, observe, heed, attend, learn, become aware of, to know, be conscious again". The term appears extensively in Rigveda and other Vedic literature. Buddhi means, states Monier Williams, the power to "form, retain concepts; intelligence, reason, intellect, mind", the intellectual faculty and the ability to "discern, judge, comprehend, understand" something.
Buddhi contrasts from manas (मनस्) which means "mind", and ahamkara (अहंंकाऱ) which means "ego, I-sense in egotism".
In Samkhya and yogic philosophy both the mind and the ego are forms in the realm of nature (prakriti) that have emerged into materiality as a function of the three gunas (ग़ुण) through a misapprehension of purusha (पुरूष) (the consciousness-essence of the jivatman). Discriminative in nature (बुद्धि निश्चयात्मिका चित्त-वृत्ति), buddhi is that which is able to discern truth (satya) from falsehood and thereby to make wisdom possible.
- Sir Monier Monier-Williams; Ernst Leumann; Carl Cappeller (2002). A Sanskrit-English Dictionary: Etymologically and Philologically Arranged with Special Reference to Cognate Indo-European Languages. Motilal Banarsidass. p. 733. ISBN 978-81-208-3105-6.
- Ian Whicher (1998). The Integrity of the Yoga Darsana: A Reconsideration of Classical Yoga. State University of New York Press. pp. 18, 71, 77, 92–95, 219, 231. ISBN 978-0-7914-3815-2.
- Jadunath Sinha (2013). Indian Psychology Perception. Routledge. pp. 120–121. ISBN 978-1-136-34605-7.
- Sir Monier Monier-Williams; Ernst Leumann; Carl Cappeller (2002). A Sanskrit-English Dictionary: Etymologically and Philologically Arranged with Special Reference to Cognate Indo-European Languages. Motilal Banarsidass. pp. 124, 783–784. ISBN 978-81-208-3105-6.