A brief, introductory talk on a subject, such as this, will naturally be expected to start with a definition. In this, I must frankly admit to some difficulty, as I do not know of any really satisfactory definition of operational research. This, however, is nothing to be abashed at. It is usually easy enough to be clear about a field of study when you are in the centre of it; the boundaries, however, are commonly diffuse—and it is with boundaries that definitions are concerned. This difficulty of precise definition can be found even with quite well-established fields such as physics or, dare I suggest, the actuarial profession.

I shall therefore be content to quote a phrase which is commonly applied to operational research, really more a description than a definition, and shall then try to expand and explain the salient points incorporated in it.