A major problem with definitions of environmental terms in commercial and real estate transaction documents is that they become overly inclusive, confusing, and unworkable. A definition of "hazardous materials" which includes virtually every substance known to man in any amount at any concentration, will be impossible to satisfy in any representation regarding the absence of hazardous materials on the property. Conversely, a representation regarding "Environmental Laws" or "Environmental Requirements" may be less than anticipated if the definition uses the "list" approach and certain key environmental laws or requirements are not included. Much clarity can be obtained in the operative provisions by using defined terms with consistent and detailed definitions. The definitions often contain the key issues in the transactions and deserve considerable attention.