The IEA Teacher Education and Development Study in Mathematics (TEDS-M) is the first large-scale international study of the preparation of primary and lower-secondary teachers. The study investigated the pedagogical and subject-specific knowledge that future primary and lower secondary school teachers acquire during their mathematics teacher education. It also examined variations in teacher education programs within and across countries. TEDS-M gathered data in 2008 from approximately 22,000 future teachers from 750 programs in about 500 teacher education institutions in 17 countries: Botswana, Canada (four provinces), Chile, Chinese Taipei, Georgia, Germany, Malaysia, Norway, Oman (secondary teacher education), the Philippines, Poland, the Russian Federation, Singapore, Spain (primary teacher education), Switzerland (German-speaking cantons), Thailand, and the United States of America (public institutions, concurrent and consecutive routes only). Teaching staff within these programs (close to 5,000 mathematics and general pedagogy educators) were also surveyed. This encyclopedia provides a resource that readers can draw from when analyzing the context-based similarities and differences that are important to keep in mind when interpreting and explaining the TEDS-M results. The encyclopedia thus strengthens the reporting of this first international assessment of teacher education. It presents a broader context within which the data collected from future teachers and their educators can be understood and interpreted. Elements of this context include information about countries' distinctive political, historical, and cultural contexts that influence policy and practice in mathematics teacher education. It also describes the organization and characteristics of teacher education in the participating countries, the institutions that teach future teachers and their staff, the programs and required field experiences, and the quality-assurance arrangements. In combination with the TEDS-M international and policy reports, the TEDS-M encyclopedia is a useful resource for policy development and further research on teacher education. Following an introduction by John Schwille and Lawrence Ingvarson, chapters in the encyclopedia include: (1) Botswana (Kgomotso Gertrude Garegae, Thabo Jeff Mzwinila, and Tuelo Martin Keitumetse); (2) Canada (New Foundland and Labrador, Nova Scotia, Québec, and Ontario) (Robert Crocker and Hervé Joduin); (3) Chile Beatrice (Avalos Davidson); (4) Chinese Taipei (Feng-Juh Hsieh, Pe-Jen Lin, Guohong Chao, and Ting-Ying Wang); (5) Georgia (Natia Mzhavanadze and Tamara Bokuchava); (6) Germany (Johannes König and Sigrid Blömeke); (7) Malaysia (Rajendran Nagappan, Nagendralingan Ratnavadivel, Mohd Mustamam Abd Karim, Othman Lebar, Ismail Kailani, and Suseela Malakolunthu); (8) Norway (Trygve Breiteig); (9) Oman (Mohammed Al Ghafri, Ali Al Abri, and Mohamed Al Shidhani); (10) Philippines (Ester B. Ogena, Filma G. Brawner, and Milagros D. Ibe); (11) Poland (Michal Sitek); (12) Russian Federation; (13) Singapore (Khoon Yoong Wong, Suat Khoh Lim-Teo, Ngan Hoe Lee, Kok Leong Boey, Caroline Koh, Jagusthing Dindyal, Kok Ming Teo, and Lu Pien Cheng); (14) Spain (Encarnación Castro Martínez and Pablo Flores Martínez); (15) Switzerland (Sandra Brandt, Fritz Oser, Horst Biedermann, Margit Kopp, Sibylle Steinmann, Samuel Krattenmacher, and Christian Brühwiler); (16) Thailand (Precharn Dechsri and Supattra Pativisan); and (17) United States of America (USA) (Peter Youngs and Erin Grogan). An appendix presents: Listings of Organizations and Individuals Responsible for TEDS-M. (Individual chapters contain references.) [The international TEDS-M team at Michigan State University (MSU) in the United States, the Australian Council for Educational Research, the IEA Data Processing and Research Center (DPC) in Hamburg, and the IEA Secretariat in Amsterdam shaped the overall TEDS-M survey and developed a framework, terminology, and design that ultimately had a strong effect on what went into these chapters.]