Schizophrenia symptoms seem to worsen and improve in cycles known as relapses and remissions.

They compete using a two-person cycle known as a tandem, with a sighted "pilot" in the front seat.

The Games took place in a four-year cycle known as the Olympiad, which was one of the ways the Greeks measured time.

The estrous cycle, also known as "season" or "heat" of a mare occurs roughly every 19-22 days and occurs from early spring into autumn.

The Akan people of West Africa have a 42-day cycle known as Adaduanan.

The number of sunspots visible on the Sun is not constant, but varies over an 11-year cycle known as the solar cycle.

Another type of lending has emerged to combat this vicious cycle, known as microlending.

The Babylonians discovered that lunar eclipses recurred in a repeating cycle known as a saros.

They produce their cooling effect via the "reverse-Rankine" cycle, also known as 'vapor-compression'.

Current vapor-compression chiller technology is based on the "reverse-Rankine" cycle known as vapor-compression.