(music) That which unfolds a single recurrent interval in a series that closes with a return to the initial pitch class.

(music theory) A sequence of bass notes at intervals of a perfect fifth lower than the previous note. In equal temperament the sequence repeats every twelve tones, forming a cycle.

The natural cycle of evaporation of water from the oceans etc, and subsequent condensation and precipitation as rain and snow

(biochemistry) A series of enzymatic reactions that occurs in all aerobic organisms; it involves the oxidative metabolism of acetyl units, and serves as the main source of cellular energy.

the cycle of water from the oceans to the atmosphere to land and back into the oceans or atmosphere.

The natural circulation of nitrogen, in which atmospheric nitrogen is converted to nitrogen oxides by lightning and deposited in the soil by rain, where it is assimilated by plants and either eaten by animals (and returned as faeces) or decomposed back to elemental nitrogen by bacteria.

(biology) The course of stages through which an organism passes from fertilized zygote until maturity, reproduction, and death.

(Irish mythology) A body of prose and verse focusing on the exploits of the mythological hero Fionn mac Cumhail and his warriors the Fianna Éireann.

(biology) the transmission of hydrogen from water to carbohydrates etc and back to water by living organisms

carbon-nitrogen-oxygen cycle