From Glossary of Meteorology
The approximately 11-yr quasi-periodic variation in the sunspot number. Sunspots begin appearing at higher solar latitudes as a cycle begins and slowly drift more equatorward, becoming more in number and larger, more complex groups as the cycle draws to solar maximum. As the cycle moves to solar minimum, sunspot development slows and locations become more sporadic, eventually going days to months without any visible sunspots. The magnetic polarity pattern associated with sunspot groups in each hemisphere will reverse at the beginning of a new solar cycle. Solar cycles are numbered, beginning with solar cycle 1 in 1755. A more recent case was cycle 24 which began in 2008 (minimum) and peaked in 2014 (maximum).
Space Weather Prediction Center, 2018: Sunspots/solar cycle. Accessed 1 October 2018. Available at https://www.swpc.noaa.gov/phenomena/sunspotssolar-cycle.
Term edited 1 October 2018.