The conceptualization of number is an integral component of mathematicalleaming in early childhood. However, as noted by Vergnaud (1987), the concept of number can be interrelated with the concept of measure. Number in its most general form is quantity. What distinguishes number from sequencing, as in rote counting, is a unit of measure distinct from a lexical item. When a child assigns a number to a collection of discontinuous items via counting, the units that the child perceives are the individual items in the collection. For a set of discrete items, children learn to determine quantity by the number of unit entities, regardless of their size or relative position. Although young children may differ in terms of the type of unit they are capable of counting (Steffe, von Glasersfeld, Richards, & Cobb, 1983), it has been proposed that in the discrete domain the processes of comparing and transforming, of incrementing and decrementing units, have a major influence on the development of numerical abstraction (Cooper, 1984; Sinclair, 1987b; Starkey & Gelman, 1982). But in addition to discrete counting, measuring may also serve as a precursor to early systems of reasoning (Sinclair, 1987b). Furthermore, the process of measuring can occur at differing conceptual levels.