Deseasonalize

Part of speech: verb

Definitions

1. Adjusting statistical figures to strip out regular fluctuations that recur at fixed times of year, so underlying trends become visible
2. Taking the effect of predictable yearly cycles out of a data series so that its underlying movement can be examined
3. Correcting measurements or numbers for recurring seasonal patterns in order to reveal the non-seasonal trend beneath them

Etymology: "Deseasonalize" is a plain modern formation: the prefix "de-", meaning "remove from" or "undo", attached to "seasonal" and the verb-forming suffix "-ize". Together they mean to remove the seasonal pattern from something, most often a set of economic or statistical figures. Economists use it when they want to see the underlying trend in data, such as retail sales or unemployment, once the regular rises and falls tied to holidays, harvests or school terms have been stripped out. The word belongs to the vocabulary of statistics rather than everyday speech, and its building blocks are much older than the coinage itself. "Seasonal" comes from Latin "season" via Old French, while "-ize" arrived in English through French and Greek to form verbs from nouns and adjectives. "De-" comes from Latin, where it meant "down from" or "away", and in English it became a productive way of reversing or removing something.