1. the empirical relation between two events, states, or variables such that change in one (the cause) brings about change in the other (the effect). See also causality.

2. in Aristotelian and rationalist philosophy, the hypothetical relation between two phenomena (entities or events), such that one (the cause) either constitutes the necessary and sufficient grounds for the existence of the other (the effect), or the one possesses the capacity to bring about the other. —causal adj.