1. Introductory. Tf we regard language activity, in its formal aspect, as the repeated selection of one from among a number of possible events—or, so as to formulate it more simply, of items from sets of items which are “at risk” under certain conditions, the total selection situation (items and conditions) varies along a cline. At one end of the scale, there are a very large number of sets, in very complex interrelations, but with very few items in each: this is grammar. At the other end, there are few sets, in simple relations, but with large inventories of items making them up: this is lexis. There is no sharp line between them, though the extremes are clearly distinct. Since patterning of the first type lends itself to much greater abstraction, we can make the theory of grammar much more powerful than the theory of lexis. So the linguist tries to bring as much as possible of linguistic form into his grammatical statements—though there is a theory of lexis too, which has a part in the total description.'