Mass: still a fascinating concept in physics

The subject matter of this article is MASS, a common word indeed to all scientists who have to deal with matter in one form or another. It is probably also a familiar word to the modem housewife, although here I suspect, that we meet the first example of confusion of for weight, a point to which we return later. The commonness, or the seemingly commonplace nature of the term, hides a profound and, in some ways, as yet unresolved conceptual difficulty that is not at all obvious or apparent to the uninitiated. It is my intention in what follows to bring to the reader some of these deep meanings that go with the seemingly simple term mass and, in the process, obliquely make an incidental, but important point, namely, that even in the traditional aspects of physics, our ideas about concepts like are still very much alive and subject to further development.