Definitions for “forest” and “woodland” are heterogeneous around the world. Great diversity and diffuse thresholds among ecosystems hinder the construction of criteria for the definition of woodlands. The focus of this review is to deconstruct structural definitions for forests and woodlands. Three fundamental conditions are proposed. A synthesis of the most relevant criteria for the definition and evaluation of forests and woodlands is presented, describing the basic functional aspects for the construction of sustainability indicators. Three conditions are defined: self-organization, dynamics and teleonomy; including different criteria: diversity, reliability and redundancy, fragmentation, connectivity, resilience and stability, and regeneration. Woodlands functioning should be the main condition for its inclusion in natural resources laws for the management and conservancy, according to the local context. Generalization of conditions for all woodlands in the world or in a particular country is unpractical and should encompass the expected functional criteria according to local context.