A system of promotion and relegation exists between the Premier League and the EFL Championship. The three lowest placed teams in the Premier League are relegated to the Championship, and the top two teams from the Championship promoted to the Premier League, with an additional team promoted after a series of play-offs involving the third, fourth, fifth and sixth placed clubs. The number of clubs was reduced from 22 to 20 in 1995, when four teams were relegated from the league and only two teams promoted. The top flight had only been expanded to 22 teams at the start of the 1991–92 season – the year prior to the formation of the Premier League.

On 8 June 2006, FIFA requested that all major European leagues, including Italy's Serie A and Spain's La Liga, be reduced to 18 teams by the start of the 2007–08 season. The Premier League responded by announcing their intention to resist such a reduction. Ultimately, the 2007–08 season kicked off again with 20 teams.
how many teams relegate from the English premier league?
The Premier league consists of 20 teams. At the end of each season the bottom three teams gets relegated to the EFL and three teams from the EFL gets promoted to the premier league.