In time series analysis, seasonality refers to:

A. The presence of trends in the data.
B. Patterns that repeat at regular intervals.
C. Random fluctuations in the data.
D. Long-term cycles in the time series.

Correct Answer: B

Seasonality is a time series feature in which data shows regular and predictable patterns that recur every year. For example, retail sales tend to peak for the Christmas season and then decline after the holidays. The term "periodicity" in time series seasonality refers to the repetition of patterns at fixed intervals.