The term Regular Season ( German regular season), derives from Old English and is primarily in North American professional sports use. There, a season is usually divided into regular season and play-offs.
The several months comprehensive "regular" season serves as a qualifier for the relatively short play-offs. Based on the Final Table of the Regular Season, the pairings for the play-offs are set.
Comparable modes can be found in European basketball, ice hockey and football leagues, where first a preliminary round is played, followed by play-offs.