A fundamental truth or law as the basis of reasoning .
Principles are the broad goals of sustainable forest management.
Criteria define a principle and provide the basis of assessing whether the goals for sustainable forest management are being achieved. A measure by which a criterion is judged by. Indicators are quantitative or qualitative variables which can be measured or described. They provide verifiable measures of change in a criterion over time. A defined measure that an aspect or component of forest management must achieve to be sustainable.