Scenario development efforts involving people from diverse disciplines tend to suffer from a communication barrier due to the different scenario-related language used in various fields and organizations. Scenario-related literature is also inconsistent; as certain terms have different or interchangeable meanings across the literature. The definitions provided below are recommended for the purpose of clarity and consistency.

Alternative Futures: different representative “future worlds” that collectively illustrate the universe of the future.

Adaptive Capacity: ability of a system to successfully accommodate impacts of change.

Cascading Events: a consecutive set of events that occur as a result of specific triggers.

Conceptual Model: a high-level conceptual representation of important assumptions, inter-component flows, states, parameters, and uncertainties; may be used as a basis for numerical models.

Discontinuities: events or consequences that cannot be extrapolated from prior actions or events and are unpredictably new.

Model Structure: conceptualization and mathematical implementation of a model.

Model: a particular combination of a model structure, parameters, and boundary and initial conditions.

Monitorable Indicators: variables that can be tracked through time to determine the occurrence of regimes, triggers, cascading events, discontinuities, and wild cards.

Parameter: characteristic property of a system that remains constant over a time duration of interest.

Regimes: shift in the persistent status of a system.

Resilience: ability of a system to maintain its structure and function when external forces are acting on it.

Risk: a measure of the probability and severity of adverse affect.

Sensitivity Analysis: assessment of how variations in specific factors (input, parameter, state etc.) affect the output (response) of a model.

Thresholds: conditions in time and space that produce notably different experiences in a system’s state or response.

Trends: patterns of behavior over time of the most critical and most uncertain variables.

Triggers: particular combination of conditions that lead to a change in a system’s regime.

Uncertainty: inability to precisely determine the true magnitude or form of system/model variables or characteristics.

State Variables: variables that describe the time-varying characteristics of a system.

Wild Cards: major surprises that have high impacts.