The Dictionary of Forestry is a revision of the 1971 Terminology of Forest Science, Technology, Practice, and Products, published by the Society of American Foresters and edited by F.C. Ford-Robertson under the authorization of the Joint FAO/IUFRO Committee on Forest Bibliography and Terminology. Since 1971, there have been substantial changes in the forestry profession — from a focus on multiple use an sustained yield of forest products to a broader, more complex context of sustaining diverse forest uses and values. These changes have modified the use of existing terms, introduced new terms, and created the need for an up-to-date dictionary that permits consistent use of professional language. The recommendation to revise the Ford-Robertson Terminology was made by the Society of American Foresters' Forest Science and Technology Board and endorsed by SAF's Council. SAF's 29 working groups were asked to contribute to the revision. Provided with subsets of terms within their fields of interest, they determined whether to retain, revise, retire, or add terms. Technical editing was done by a subcommittee of the board, whose suggested changes were returned to the working groups. Once the submissions were compiled, the subcommittee resolved issues of duplicate definitions of the same term by different working groups, and the compilation of all terms was returned to the working groups for final review. We hope this dictionary will help students, professionals, and the public — all those interested in the science, management, and conservation of forests — communicate technically with precision, clarity, and consistency. As with all language, the vocabulary of forestry is dynamic, and the terms and definitions complied here reflect current professional acceptance and use. Realizing that this work is ongoing, the editor and publisher welcome your general comments and questions as well as information on perceived errors and omissions.