Cycle

Circulation generally stands for

a regularly recurring sequence of events, see periodicity
in physiology for the blood circulation , the glymphatic system and the enterohepatic circulation
in economics for the economic cycle
in thermodynamics for the cycle, see thermodynamic cycle
in electrical engineering for the circuit
in ecology for the material cycle
in politics for the constitutional cycle
open or closed circuit in the hydraulics, see hydraulic pump # circuit concepts

See also:

Wikiquote: Circulation Quotes

Wiktionary: cycle - explanations of meanings, word origins, synonyms, translations