Question: How many breaks of serve is required to win a set?
About the article "Tennis", section "Special point terms".

Candidate passages:
The concept of productive system hours (PSH) has been used in forestry in Austria and by extension to other work.
It includes time for breaks and can be used to calculate how long a task may take to be done including required recovery times from physically strenuous work as well as legally required breaks or other human interactions.
If it includes 15 min breaks it is written as (PSH15).
A related concept is productive machine hours (PMH). 
The chair umpire was Lars Graff of Sweden.
Both players began the match strong with the first eleven games of the first set going to serve.
However, with Federer serving at 5-6, Roddick broke to take the first set.
Perhaps the most critical moment of the match was in the second set tiebreaker when Roddick led 6-2 with four set points to take a commanding lead.
Federer subsequently reeled off six consecutive points to even the match at one set a piece.
The most memorable moment of the tiebreaker is when Roddick served at 6-5 set point and botched a back-hand volley wide to even up the tiebreaker.
The third set was a tight affair without any breaks of serve for the second consecutive set.
The tiebreaker went to Federer who was now only one set away from breaking Pete Sampras' all-time Grand Slam record.
Roddick, however, surprised many by breaking Federer in the fourth set to even the match and take the Wimbledon final to a decisive fifth set for the third consecutive year.
The fifth set would turn out to be a historic battle.
Both players were dominant on serve throughout the first sixteen games without a single break point opportunity to be had.
A moment of crisis arrived for Federer with him serving at 8-8 down 15-40, but he rallied to deny Roddick the opportunity to serve for the match.
There was not another break opportunity until Roddick served at 14-15 and Federer broke him, for the first time in the entire match, to win a record shattering fifteenth Grand Slam championship.
This set remains the longest fifth set in a Grand Slam final. 
"Serviam", meaning "I will serve", is a major part of Ursuline life.
Girls are required to perform a set number of hours each semester, adding up to a total of 100 hours by graduation.
However, most students easily exceed the required number of hours by far.
Services hours can be accumulated over all breaks and holidays, including summer vacation between school years, and seniors are set up with local charities, hospitals, and public schools to perform community service on Monday mornings in lieu of classes.
During the 2005-2006 school year, students performed over 630,000 hours of service in both local and international communities. 
The 2012 US Open Men's Singles final was the championship tennis match of the Men's Singles tournament at the 2012 US Open.
It pitted then-world No.
3 Andy Murray against world No.
2 and defending champion Novak Djokovic in a Grand Slam final for the second time.
Murray defeated Djokovic in five sets to win the match.
It was the equal-longest US Open men's final in history, lasting four hours and fifty-four minutes (equalling the 1988 US Open final played by Ivan Lendl and Mats Wilander), and the equal second-longest men's final in the Open era, only behind the aforementioned 2012 Australian Open final.
By winning the 2012 US Open, Murray became the first British man since Fred Perry in 1936 to win a Grand Slam singles title, and the first British man in the Open Era to do so.
This was the most famous match in the rivalry between the two players.
It also marked a milestone for Murray, as it was his 100th match win at a grand slam tournament.
This match featured the longest ever first set (and the longest ever tiebreak) in a men's championship match; the 87-minute first set, won by Murray, included four breaks of serve in the first four games of the match, a 54-shot rally in the sixth game, and the 24-minute tiebreak which lasted up until 12–10; additionally, the tiebreak included two 30-shot rallies.
Murray required six set points to win the first set, and required five sets to win the match.
Murray said that a toilet break at the end of the fourth set helped him to restore his concentration after Djokovic took the third and fourth sets. 
The first match of the day began with the group A as Magdaléna Rybáriková looking on winning her first match in the tournament and Shahar Pe'er playin her first match.
Pe'er comfortably won the first 6–1 by serving 74% of first serve and converting her 2 break points in the set.
The second looked the same as the first in the beginning, leading Rybáriková 4–1 with two breaks of serve, however Rybáriková change her style of play as she became more aggressive to win the next 4 games to lead 5–4, but it was too late as Pe'er stopped her run to hold for 5–5, and then edged the tiebreak 7–4.
Shahar Pe'er match with Marion Bartoli will declare the group's representative in the Semifinals.
The match was followed by Frenchwoman Aravane Rezaï and Melinda Czink of group D. Czink made a good start and led the first set 2–0, however Rezaï returned the favor by taking the next two games, they then both held serve at 3–3.
However at the 7th game, in Czink' serve she scored a double faults on break point that eventually led to Rezaï claiming a 4–3 lead, and that was proven enough as she hold serve and broke again to win the set 6–3.
The second set looked like it was going to a decider as Rezaï piled up the double faults and Czink improves her serve to take a 5–1 and a set point, however her error on the forehand saw that set point lost.
from then on as fast as she took the 5–1 lead in vanished even faster as Rezaï won the next 6 games and the set 7–5 and the match.
Rezaï will now be the first to advance to the semifinals with two wins.
The match between María José Martínez Sánchez and Ágnes Szávay followed.
Szávay took the first set comfortably 6–4.
However in the second as the same as her match with Stosur, she cost herself the match as she committed 7 double faults to give the set to Martínez Sánchez 6–4.
The deciding set was a one way affair as Martínez Sánchez blasted Szávay of the court winning the last set 6–0.
This win meant that Martínez Sánchez match with Samantha Stosur will declare the group's representative in the Semifinals.
The last match saw Kimiko Date-Krumm taking on Anabel Medina Garrigues.
In the first set Krumm broke Garrigues serve early but failed to keep the advantage; however in the 9th game Date-Krumm broke the Medina Garrigues serve and eventually won the set 6–4.
The second set then saw the two players trade breaks in the first four games, and then hold their respective serves for a 3–3.
As Date-Krumm became more aggressive she broke the Medina Garrigues serve to lead 4–3 then broke again to win the set and match 6–3.