From Wikipedia on 10/12/12:
Etymology
From Late Latin cyclus, from Ancient Greek κύκλος (kyklos), reduplicated form of a Proto-Indo-European *kʷékʷlos (“circle, wheel”). Cognates include Sanskrit चक्र (cakrá), Latin colus, Old English hwēol (English wheel), English ancillary
An interval of space or time in which one set of events or phenomena is completed.
A complete rotation of anything.
A process that returns to its beginning and then repeats itself in the same sequence.
Book Excerpts:
“Don’t be fooled by system cycles. All negative feedback loops create oscillations–some large, some small. For some reason, many people are unable to deal with or believe in cyclical patterns, especially if the cycles are more than two or three years in length. If the economy has been growing steadily for the last four years, nearly everyone will be optimistic. They simply project their recent experience ahead into the future, forgetting that a recession becomes more likely the longer the boom continues. Similarly, everyone is gloomiest at the bottom of a recession, just when rapid growth is most likely.”
– Draper Kauffman, Jr., in Systems 1: An Introduction to Systems Thinking