【Abstract】Humor plays a very important role in our life. It can adjust social relationship， amuse one’s mood， enrich one’s life and exhibit one’s wisdom. Sitcom is one of the most popular programs in modern society and in it humor plays an essential role. This study investigates the humorous dialogues in the American situation comedy Friends， and discusses how the humor is generated.
　　【Key words】humor； sitcom； Friends
　　Introduction
　　A situation comedy， or sitcom， is a genre of comedy telling the stories of characters who share a common environment （home or workplace） with often-humorous dialogue. It is originally devised for radio but today typically found on television. As is indicated by the name， situation comedies intend to be humorous so as to amuse the audience. This thesis aims at investigates humorous language in the American sitcom Friends and discusses how the humor is created.
　　1. Literature review
　　1.1 Situation comedy and its main features
　　The Wikipedia’s definition of a situation comedy is “a genre of comedy that features characters sharing the same common environment， such as a home or working space， with humorous dialogue.” Situation comedy，， originated in U.S. radio in the 1920s and later took the form of television shows.
　　A sitcom in its nature is a comedy and is meant to be humorous. Sitcoms usually revolve around a same cast of characters and the stories take place in a common situation. Another important feature is the laugh track. To reduce costs， some producers may not use live audiences when shooting and use pre-recorded laughter instead. Sitcoms is also fixed length of episodes. Each episode is from 20 to 30 minutes. For American sitcoms， each season usually contains 23 to 24 episodes .
　　1.2 Definition of humor
　　According to Attardo （1994）， the English word “humor” or “humour” is derived from the Latin word， in the beginning it is a medical term which originally means “liquid” or “fluid” or “moisture”. In early Western physiological theory established by Hippocrates （460-370 B.C）， humor was regarded as one of the four fluids （blood， phlegm， choler， melancholy） of the body which were considered to determine a person’s features. However， as time passing by， “humor” gradually loses its original meaning and gets meaning in the field of aesthetics and literature with sense of modern humor. At the end of 18th century， in Oxford English Dictionary， “humor” already had the modern meaning.