ahamkara

Ahaṃkāra (अहंकार) is a Sanskrit term that refers to egoism, that is the ego of one's self, the identification of one's own ego. It is the belief of self-consciousness or "I-ness" and the tendency to identify oneself with external phenomena, "The I-maker." Even though it is not discussed in great detail in the Bhagavad Gita, Lord Krishna says to Arjun that it must be removed.
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Ahamkara (Sanskrit) [from aham ego, I + kara maker, doer from the verbal root kri to do] I-maker; conception of egoity or I-am-I-ness. In its lower aspect, the egoistical and mayavi principle, born of avidya (ignorance), which produces the notion of the personal ego as being different from the universal self. In Sankhya philosophy ahamkara is the third emanation: from prakriti (primal nature or substance) issues mahat (the great), standing for universal mind, which in turn produces ahamkara, selfhood, individuality; from ahamkara come forth the five tanmatras, the subtle forms of the elements or principles and "the two series of sense organs" (Samkhya-Sutra 1:61).
In the Bhagavad-Gita (7:4), prakriti manifests in eight portions -- "earth, water, fire, air, ether [space: kham-akasa], mind [manas], understanding [buddhi] and egoity, self-sense [ahamkara]" -- all of which relate to the object side, which gives an erroneous sense of identity or egoity.
As universal self-consciousness, ahamkara has "a triple aspect, as also Manas. For this conception of 'I,' or one's Ego, is either sattwa, 'pure quietude,' or appears as rajas, 'active,' or remains tamas, 'stagnant,' in darkness. It belongs to Heaven and Earth, and assumes the properties of either" (SD 1:335n).