A circaian rhythm is an approximate daily periodicity, a roughly-24-hour cycle in the biochemical, physiological or behavioral processes of living beings, including plants, animals, fungi and cyanobacteria. The term "circadian", coined by Franz Halberg, comes from the Latin circa, "around", and diem or dies, "day", meaning literally "approximately one day." The formal study of biological temporal rhythms such as daily, tidal, weekly, seasonal, and annual rhythms, is called chronobiology.