I remember being in a linguistics class many years ago and being asked to define, in real time, Table and Chair. Every single person in the room knew precisely what a table and chair were, had a clear mental picture of what one should entail, but was completely stymied when it came to delineating limiting characteristics. The concepts occupy more of a loose range than a strictly proscribed limit. When you get right down to it. I suspect that most concepts are that way. You and I believe, when we are talking, that we both agree upon the limits of a concept, but that is rarely so, it's the central idea that we agree on, and the limits are subject to a case by case review. Primarily, I believe that a salad is composed of cold foods, tossed in a dressing rather than cooked in a sauce, but that may be just my perception. Marya