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**Periodicity** or **periodic** may refer to:

## Mathematics

- Bott periodicity theorem, addresses Bott periodicity: a modulo-8 recurrence relation in the homotopy groups of classical groups
- Periodic function, a function whose output contains values that repeat periodically
- Periodic mapping

## Physical sciences

- Periodic table of chemical elements
- Periodic trends, relative characteristics of chemical elements observed
- Redshift periodicity, astronomical term for redshift quantization

## Other uses

- Fokker periodicity blocks, which mathematically relate musical intervals
- Periodic acid, a different pronunciation and different meaning of the word
*periodic* - Principle of periodicity, a concept in generally accepted accounting principles
- Quasiperiodicity, property of a system that displays irregular periodicity

## See also

- Aperiodic (disambiguation)
- Cycle (disambiguation)
- Frequency (disambiguation)
- Period (disambiguation)
- Periodical
- Seasonality, periodic variation, or periodic fluctuations