Hay-yah (Heb.) One of the metaphysical human “Principles”. Eastern Occultists divide men into seven such Principles; Western Kabbalists, we are told, into three only—namely, Nephesh Ruach and Neshamah. But in truth, this division is as loose and as mere an abbreviation as our “Body, Soul, Spirit ”. For, in the Qabbalah of Myer (Zohar ii.,141 b., Cremona Ed. ii., fol. 63 b., col. 251) it is stated that Neshamah or Spirit has three divisions, “the highest being Ye’hee-dah (Atmâ) the middle, Hay-yah (Buddhi), and the last and third, the Neshamah, properly speaking (Manas) ”. Then comes Mahshabah, Thought (the lower Manas, or conscious Personality), in which the higher then manifest themselves, thus making four; this is followed by Tzelem, Phantom of the Image (Kama-rupa in life the Kamic element); D’yooq-nah, Shadow of the image (Linga Sharira, the Double); and Zurath, Prototype, which is Life—seven in all, even without the D’mooth, Likeness or Similitude, which is called a lower manifestation, and is in reality the Guf, or Body. Theosophists of the E. S. who know the transposition made of Atmâ and the part taken by the auric prototype, will easily find which are the real seven, and assure themselves that between the division of Principles of the Eastern Occultists and that of the real Eastern Kabbalists there is no difference. Do not let us forget that neither the one nor the other are prepared to give out the real and final classification in their public writings.
Source: H.P.Blavatsky - The Theosophical Glossary