जीवनाज्जीव इत्युक्तोऽहंभावः स्यात्त्वहंतया ।बुद्धिर्निश्चायकत्वेन संकल्पकलनान्मनः
In plain words
From jīvana, 'living', he is called jīva; through ahaṃtā, he is the sense of 'I'; through its function of determining, he is buddhi; through the fashioning of saṃkalpa, he is manas.