The 14th International Conference on Developments in Language Theory (DLT 2010) was held in London, Ontario, Canada on the beautiful campus of the University of Western Ontario. It was a four-day conference starting August 17 and ending August 20, 2010. The DLT conference series is one of the major international conference series in language theory. It started in Turku, Finland in 1993. Initially, it was held onceeverytwoyears. Since2001,ithasbeenheldeveryyear,oddyearsinEurope and even years in other continents. The papers submitted to DLT 2010 were from 27 countries all over the world, which include Australia, Austria, Belgium, Canada, Czech Republic, Denmark, Finland, France, Germany, Hungary, Iceland, India, Italy, Japan, Latvia, Moldova, The Netherlands, Poland, Portugal, Russian Federation, S- vakia, South Korea, Spain, Sweden, Tunisia, UK, and the USA. Each paper was reviewed by three referees and discussed by the members of the Program C- mittee. Finally, 32 regular papers were selected by the Program Committee for presentation at the conference. There were six invited talks given at the c- ference. They were given by (in alphabetic order) Dora Giammarresi (Rome), MarkusHolzer (Giessen), OscarIbarra(Santa Barbara),Lila Kari(London,- tario), Michel Rigo (Liege), and Grzegorz Rozenber (Leiden). In addition, there were six posters on display at the conference. This volume includes all the 32 contributed papers, the papers or abstracts from the 6 invited speakers, and a 2-page abstract for each of the 6 poster papers. Wewarmlythankalltheinvitedspeakersandalltheauthorsofthesubmitted papers. Their e?orts were the bases of the success of the conference.