Support surfaces remain an integral component of pressure injury prevention and treatment. Recent research and new technologies coupled with new standards testing created a need for revision of past terms and definitions related to support surfaces. These terms and definitions have been developed to provide a common understanding of terms that refer to basic physical concepts, design considerations, and product characteristics. Thus, the purpose of this document is to provide a glossary of terms and definitions that are specific to the language used within the Support Surface Standards Initiative, and serve as a lexicon to facilitate and provide clarity of understanding regarding performance evaluation and the standardized testing protocols. Based on the work of the Support Surface Standards Initiative (S3I) of the NPUAP, new terms and definitions were added, and all were compiled into an alphabetical list to facilitate ease of use. While this is a comprehensive and inclusive list, periodic review and revision is required. The bibliography, of necessity, includes classic references for terms for which the definitions have not changed. The foundational definition of a support surface used in this document is: "A specialized device for pressure redistribution designed for management of tissue loads, micro-climate, and/or other therapeutic functions (e.g. any mattresses, integrated bed system, mattress replacement, overlay, or seat cushion, or seat cushion overlay)."