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.

Initialism of Catholic Youth Organization.

(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.

An early particle accelerator in which charged particles were generated at a central source and accelerated spirally outward through a fixed magnetic field and alternating electric fields.

(pathology) Inflammation of the urinary bladder.

Alternative spelling of cyclopaedia

(cycling) A device that counts the revolutions of a bicycle wheel in order to indicate distance travelled. / An instrument for measuring circular arcs.

(US) a domestic underground shelter used as protection from severe winds

(archaic) The circle or compass of the arts and sciences (originally, of the seven so-called liberal arts and sciences); circle of human knowledge. / (archaic) An encyclopedia.