Resilience is the capacity of a socioecological system (SES) to withstand disturbance and remain in a particular state space. It has multiple meanings: as a metaphor for sustainability, as a property of dynamic models, and as a measurable quantity in field studies. However, operational indicators of resilience have received little attention in the literature. To assess resilience, one must specify the system configuration and disturbances of interest. This paper compares resilience properties in two contrasting SES: lake districts and rangelands, focusing on three features: (a) the ability of an SES to stay in its domain of attraction, related to slowly changing variables or disturbance regimes; (b) the ability of an SES to self-organize, related to endogenous reorganization; and (c) the adaptive capacity of an SES, related to mechanisms for learning and innovation. Resilience is often used with "adaptive capacity," which has multiple meanings. Clear and measurable definitions of resilience are crucial for ecosystem management. Resilience is defined as the capacity of a system to undergo disturbance and maintain its functions and controls. It is measured by the magnitude of disturbance the system can tolerate and still persist. This definition contrasts with Pimm's definition, which emphasizes resistance and recovery from disturbance. Resilience and resistance are both important for persistence. Resilience is the ability of a system to withstand disturbance and remain in its state space, while resistance is the amount of external pressure needed to cause disturbance. Resilience can be desirable or undesirable, as some system states, like polluted water or dictatorships, can be highly resilient. Sustainability is an overarching goal that includes assumptions about desirable system states. The adaptive cycle is a key metaphor for understanding resilience, consisting of four phases: rapid growth and exploitation (r), conservation (K), collapse or release (Ω), and renewal or reorganization (α). Resilience changes throughout the cycle, with different aspects prominent at different phases. The adaptive cycle is a useful metaphor but not a testable hypothesis. It helps classify SES dynamics and generate testable explanations for a wide range of situations.Resilience is the capacity of a socioecological system (SES) to withstand disturbance and remain in a particular state space. It has multiple meanings: as a metaphor for sustainability, as a property of dynamic models, and as a measurable quantity in field studies. However, operational indicators of resilience have received little attention in the literature. To assess resilience, one must specify the system configuration and disturbances of interest. This paper compares resilience properties in two contrasting SES: lake districts and rangelands, focusing on three features: (a) the ability of an SES to stay in its domain of attraction, related to slowly changing variables or disturbance regimes; (b) the ability of an SES to self-organize, related to endogenous reorganization; and (c) the adaptive capacity of an SES, related to mechanisms for learning and innovation. Resilience is often used with "adaptive capacity," which has multiple meanings. Clear and measurable definitions of resilience are crucial for ecosystem management. Resilience is defined as the capacity of a system to undergo disturbance and maintain its functions and controls. It is measured by the magnitude of disturbance the system can tolerate and still persist. This definition contrasts with Pimm's definition, which emphasizes resistance and recovery from disturbance. Resilience and resistance are both important for persistence. Resilience is the ability of a system to withstand disturbance and remain in its state space, while resistance is the amount of external pressure needed to cause disturbance. Resilience can be desirable or undesirable, as some system states, like polluted water or dictatorships, can be highly resilient. Sustainability is an overarching goal that includes assumptions about desirable system states. The adaptive cycle is a key metaphor for understanding resilience, consisting of four phases: rapid growth and exploitation (r), conservation (K), collapse or release (Ω), and renewal or reorganization (α). Resilience changes throughout the cycle, with different aspects prominent at different phases. The adaptive cycle is a useful metaphor but not a testable hypothesis. It helps classify SES dynamics and generate testable explanations for a wide range of situations.