Skandhas (Sanskrit, «group»; Pali, khandhas means aggregate, quantity and multitude. In Buddhism the five aggregations that constitute the human appearance (nama-rupa) mental and physical existence, which are
(i) rupa, material composition;
(ii) vedana, sensing, including sensing through the sixth sense of mental impressions;
(iii) samjna (Pali, sanna), perception;
(iv) samskara (pali, sankhara), mental formations, producing character;
(v) vijana (Pali, vinnana), consciousness. They are constantly in the process of change, and do not constitute self (Anatta [anatman]).
The five skandhas are also grouped into three: rupa, cetasika (conditioning factors of consciousness, (ii), (iii) and (iv) above), and citta (state of consciousness); or even simply as rupa plus nama, that is, rupanama.
The alternative organizations simply serve as a reminder that there is nothing fixed or substantial in the skandhas so it can be named as such. A.G.H.
Bowker, John, The Oxford Dictionary of World Religions, New York, Oxford University Press, 1997, p. 907