A cycle is anything round, in the physical sense (e.g. a bicycle) or in a temporal sense (e.g. the cycle of the seasons). Cyclic or cyclical are the adjective forms. Pages about cycles include:

• Cycle studies for interdisciplinary cycle research. See also Foundation for the Study of Cycles and list of cycles
• Cyclical patterns in history.
• The Indiction cycle is a Roman tax cycle of 15 years.
• In physics, the CNO cycle is a type of fusion reaction. The Rabi cycle is a term in quantum optics.
• The duty cycle in telecommunication.
• The Rapid Update Cycle for weather forecast.
• The Milankovitch cycles in paleo-climatology.
• The Boyd cycle in military strategy.
• The Nuclear fuel cycle.
• Operation Cycle during World War II.
• Top cycle, a notion in voting systems.
• Hitting for the cycle in Baseball.
• The dynastic cycle in Chinese political theory.
• The Sexagesimal cycle in Chinese philosophy and calendar.
• The Instruction cycle in a CPU.

• In arts,
  • In music: Interval cycle and song cycle in music. Also in music, the cycle of fifths.
  • A literature cycle, e.g. The Ring Cycle (more examples there).
  • A sonnet cycle (examples there).
  • The Cremaster Cycle, a sequence of five films by Matthew Barney.
  • The Baroque Cycle, a series of books written by Neal Stephenson.
  • The Pendragon Cycle, a series of books written by Stephen R. Lawhead.
  • Northern Homily Cycle, a poem from the 14th century
  • Break The Cycle, Staind's 3rd album.

• In astronomy,
  • The eclipse cycle and the Saros cycle.
  • The solar cycle related to sunspots.
  • The full moon cycle.
  • The Metonic cycle in calendars.
  • The Sothic cycle in the ancient Egyptian calendar.

• Bicycle related meanings include
  • Bicycle, tricycle and unicycle. See also Freight bicycle.
  • Motorcycle.
  • The Paris-Roubaix Cycle Race.
  • A cycle path and (in Britain), the Sea to Sea Cycle Route and the National Cycle Network.
  • The Wright Cycle Company which funded the brothers' Wright aviation experiments.

• Biological meanings include
  • The life cycle;
  • The reproductive cycle;
  • The cell cycle;
  • The sleep cycle;
  • The lytic cycle related to viruses;
  • The honeybee life cycle;
  • The eel life cycle;
  • The earthworm organic cycle;
  • The urea cycle; and
  • The Menstrual cycle.
  • The human sexual response cycle

• Chemical meanings include
  • A series of chemical reactions. See e.g. Citric acid cycle, the Born Haber cycle or the Calvin cycle.
  • Biogeochemical cycles such as the water cycle and the Ozone-oxygen cycle (see list there).
  • A cyclic compound. See also alicyclic compound.

• In engines,
  • The Otto cycle, the Diesel cycle, the two-stroke cycle, the Miller cycle and the Atkinson cycle in cars;
  • The Carnot cycle, Rankine cycle, Stirling cycle and Ericsson Cycle in heat engines;
  • The Brayton cycle in a gas turbine;
  • The combined cycle in power plants;
  • The Refrigeration cycle
  • Rockets,
    • The liquid air cycle engine
    • The expander cycle
    • The Gas-generator cycle
    • The Staged combustion cycle
    • The Pressure-fed cycle

• In finance,
  • A cash conversion cycle.
  • The related notions of product life cycle management, Life cycle cost analysis, life cycle assessment and systems development life cycle.
  • Virtuous circle and vicious circle.
  • A business cycle, e.g. the RBC.
  • A cycle count is an inventory management procedure.

• Mathematical meanings include
  • A cycle in a permutation. See also Cyclic permutation.
  • A cyclic group.
  • A cycle and a Hamiltonian cycle in graph theory. See also cycle space and Floyd's cycle-finding algorithm.
  • A cycle is an element of a homology class. See also Hodge cycle.
  • The Limit-cycle in dynamical systems, e.g. the Lotka-Volterra cycle.
  • A cycle matroid.
  • A cyclic order.

See related meanings under period.