perusjaksona

Perusjaksona is the translative form of the Finnish noun perusjakso, meaning “as the base period” or “as the reference period.” The term is used mainly in statistics, time-series analysis, climate science, epidemiology, and economics to designate the period against which changes, anomalies, or indices are measured. By defining a perusjakso, researchers establish a baseline that enables comparisons over time and across data sets.

In practice, a sentence such as “Tutkimuksessa perusjaksona käytettiin vuotta 2010” illustrates the concept: the year 2010 served as the base period for calculations. The exact interpretation of perusjaksona can vary by field, and some contexts may use synonyms such as viitejakso or referenssikausi to express a similar baseline.

Linguistically, perusjaksona appears in the translative case to denote the function of the period in the analysis—“as a base period.” The corresponding nominative form is perusjakso, and other cases (e.g., perusjaksona, perusjaksoa) adapt the phrase to different syntactic roles. The term is often paired with explicit interval notation, such as perusjakso 2010–2014, to avoid ambiguity.

See also: baseline, reference period (viitejakso, referenssikausi), time-series anomaly, index construction.