Question: do you have to win a tennis set by 2

Answer: Yes, A tennis match is composed of points, games, and sets. A set consists of a number of games (a minimum of six), which in turn each consist of points. A set is won by the first side to win 6 games, with a margin of at least 2 games over the other side (e.g. 6--3 or 7--5). There is usually a tie-break if the set is tied at six games per player. A match is won when a player or a doubles team wins the majority of prescribed sets. Matches employ either a best-of-three or best-of-five set format. The best-of-five set format is typically only played in the men's singles or doubles matches at Grand Slam and Davis Cup matches.