Mastering Python for Finance - Second Edition

Types of stationary processes

These are a number of definitions of stationarity that you may come across in time series studies:

• Stationary process: A process that generates a stationary series of observations.
• Trend stationary: A process that does not exhibit a trend.
• Seasonal stationary: A process that does not exhibit seasonality.
• Strictly stationary: Also known as strongly stationary. A process whose unconditional joint probability distribution of random variables does not change when shifted in time (or along the x axis).
• Weakly stationary: Also known as covariance-stationary, or second-order stationary. A process whose mean, variance, and correlation of random variables doesn't change when shifted in time.