Kellokäyrä

Kellokäyrä (literally clock curve) is a Finnish term used descriptively to refer to a curve that represents how a variable changes over the course of a 24-hour clock. It is not a formal technical term with a single canonical definition; its precise meaning depends on context.

In practice, the term appears in Finnish education, popular science, and some applied fields to visualize diurnal or circadian patterns. Examples include activity levels, energy use, or physiological measures plotted against clock time.

A kellokäyrä is typically drawn with time of day on the horizontal axis from 0 to 24 hours and the variable of interest on the vertical axis. The resulting shape may be periodic, often showing peaks in daytime and troughs at night, but it can take other forms depending on the phenomenon studied.

Because it is a general, non-technical description, kellokäyrä is best understood from concrete contexts; it is related to concepts such as circadian rhythm, diurnal variation, and time-series visualization.