ABSTRACT
This chapter begins by noting some of the different kinds of numbers children commonly encounter and the different ways in which they encounter them. In research on children's understanding of numbers, "number" is used in all of the ways and sometimes considerable confusion results from intermingling them. An important relationship that holds between all the sets that belong to the same cardinal number class is that their elements can be put into one-to-one correspondence with each other. Ordinal numbers are used to designate an individual element by its position within a set rather than to quantify the set as a whole. Both the impressive achievements that young children make in learning about counting numbers and the persisting difficulties that many children have with other sorts of numbers are important parts of the story of how children learn about numbers. The chapter also presents an overview of the key concepts discussed in this book.
