In physics and mathematics, the term ergodic relates to or denotes systems or processes with the property that, given sufficient time, they include or impinge on all points in a given space and can be represented statistically by a reasonably large selection of points. A key reason to consider whether a process is ergodic is to determine if, given enough time, the process passes through all possible states with equal probability.

In economics, the term refers to a stochastic process whose statistical properties can be deduced from a single, sufficiently long, random sample of the process. The reasoning is that any collection of random samples from a process must represent the average statistical properties of the entire process. In other words, regardless of what the individual samples are, a birds-eye view of the collection of samples must represent the whole process.