A clear and consistent definition of “protected” or “conserved” is needed to establish priority values and required mechanisms for implementation of 30x30 for addressing the biodiversity and climate crises. The definition must be functional, such that it can be translated to assessing the qualification of any particular parcel on land or water in advancing the goal of 30x30. Last, the definition must be general enough that it is applicable to the variety of stakeholders involved in a national effort. A multidisciplinary team from across Defenders of Wildlife developed a definition that we believe meets those requirements for the biodiversity and climate purposes of 30x30, as detailed in this document.