Dhatu

Dhātu: 'elements', are the ultimate constituents of a whole.
I The 4 physical elements dhātu or mahā-bhūta popularly called earth, water, fire and wind, are to be understood as the primary qualities of matter. They are named in Pāli: pathavī-dhātu, āpo-dhātu, tejo-dhātu, and vāyo-dhātu In Vis.M XI, 2 the four elements are defined thus:,Whatever is characterized by hardness thaddha-lakkkhana is the earth or solid-element; by cohesion ābandhana or fluidity, the water-element; by heating paripācana the fire or heat-element; by strengthening or supporting vitthambhana the wind or motion-element. All four are present in every material object, though in varying degrees of strength. If, for instance, the earth element predominates, the material object is called 'solid', etc. 
==References==
Maha Thera Nyanatiloka. Manual of Buddhist Terms and Doctrines, Buddhist Publication Society, first edition 1952. 
Category:Pali terms