Products that are not available in certain seasons of the year or products that are available throughout the year, but the associated quantity and fluctuation of prices are referred to as seasonal products. Common examples of seasonal products are fashionable clothes, beverages, etc. More information in: Pricing Strategies in the multi-channel retail of seasonal products.
In time series data, seasonality is the presence of variations occurring at specific regular intervals of less than one year, such as weekly, monthly or quarterly. Seasonality can be caused by several factors, such as weather, holidays, and vacations , and consists of recurrent, periodic, and usually regular and predictable patterns at levels of a time series. Seasonal fluctuations in a time series can be contrasted with cyclic patterns. The latter occurs when the data show increases and falls that are not of a fixed period. These fluctuations are usually due to economic conditions and are often related to the "economic cycle". The time period usually extends beyond one year and fluctuations are usually at least two years.
Organizations that face seasonal variations, such as ice cream vendors, are often interested in knowing their performance in relation to normal seasonal variation. Seasonal variations in the labour market can be attributed to the entry of school drop-outs into the labour market, as they seek to contribute to the labor force during their vacations or at the end of their schooling. These regular changes are of less interest to those who study employment data than the changes that occur because of the underlying state of the economy; His focus is on how unemployment has changed in the workforce, despite the impact of regular seasonal variations.