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.
Source:
Bowker, John, The Oxford Dictionary of World Religions, New York, Oxford University Press, 1997, p. 907