This paper explains the economic conception of water - how economists think about water. It consists of two main sections. First, it reviews the economic concept of value, explains how it is measured, and discusses how this has been applied to water in various ways. Then it considers the debate regarding whether or not water can, or should, be treated as an economic commodity, and discusses the ways in which water is the same as, or different than, other commodities from an economic point of view. While there are some distinctive emotive and symbolic features of water, there are also some distinctive economic features that make the demand and supply of water different and more complex than that of most other goods.