These words denote the result of processes through which things or particles are gathered together. Pile suggests that the things which are gathered were brought together, usually by a person, rather than accumulated by chance or natural processes. It further suggests that the accumulated things were placed in some sort of order, one on top of the others, for example, or in layers. Finally, the things in a pile , such as the blocks in a pile of building blocks, are usually all of the same kind and, more than likely, of about the same size and shape.

Heap implies a more casual gathering of things than pile. The things, which eventually take the form of a mound, are thrown together carelessly or haphazardly, and there is usually no evidence in a heap of selection or special arrangement: a heap of old clothes in the attic. Agglomeration , even more than heap , suggests a chance coming together of its parts, those parts being heterogeneous and not compacted, connected or consistent: a room that was an agglomeration of so many different styles of decorating that it seemed more the work of an eccentric than of an eclectic.

A mass is an assemblage of things that, together, make up a single body. There is in this word a definite indication of adherence or coherence of the individual parts or objects and a suggestion that the final accumulated mass has no definite shape but is relatively large in size: a mass of clay; a mass of flowers.