periódus

Periódus is a term used in several disciplines to denote a fixed length of time or a distinctive division within a sequence. Derived from the Latin periodus, the word appears in Hungarian and other languages as the equivalent of “period” or “periods.” In different contexts, a periódus may refer to a cyclic interval, a specific row in a table, or a subdivision in history or music.

In general usage, a período is the time required for a cyclic event to repeat. Examples include the orbital period of a planet, the period of a pendulum, or the period of a wave. The relation between period and frequency is given by T = 1/f, where T is the period and f the frequency.

In chemistry, particularly within Hungarian terminology, a periódus denotes a horizontal row of the periodic table. There are seven periods in the standard table. Elements within the same periódus share a common outer-shell structure and are arranged from left to right as electrons fill the same principal quantum number in their valence shells.

In geology, a geological periódus is a subdivision of the geologic time scale within an era. Examples include the Cambrian, Jurassic, and Paleogene. Periods are defined by stratigraphic markers and are usually measured in millions of years, reflecting major changes in fossil assemblages and Earth’s systems.

In music theory, a periódus is a complete musical unit typically formed by two phrases that end with a cadence, giving a sense of closure. Periods can be parallel or contrasting and are central to the phrasing and structure of tonal music.