The four components of a time series are trend, seasonality, cyclical patterns, and random noise or irregularity. Trend refers to a long-term upward or downward movement in the data. Seasonality represents regular variations that occur at fixed intervals of time. Cyclical patterns are fluctuations that occur due to economic or business cycles. Random noise or irregularity represents the unpredictable variations in the data that are not accounted for by the other components.