number of deities : nirukta 7.5

"there are three deities only says the etyomologists: 1) agni, whose sphere is earth; 2) vayu or indra whose sphere is atmosphere ; 3) sun, whose sphere is heaven. of these each receives many appellations on account of his supereminence , or the diversity of his function, just as priest, although he is one is called sacrificer ( hotr ), the director of sacrifice ( adhvaryu ), the possessor of sacred lore ( brahma ) and the chanter ( udgatr). or else they may be distinct for their panegyrics as well as their appellations are distinct as to view that one receives many appellations on account of diversity of functions, ( it may be remarked that ) many men can also do the actions divided among themselves. with regard to it, community of jurisdiction and enjoyment should be noted as for instance community of men and gods with regard to earth. community of enjoyment is seen in following, i.e the enjoyment of earth by clouds together with air and sun and of other worlds together with agni. there everything is like kingdom of man also."