Over the years during which fluid filtration systems have been developing, many terms have come into use for descriptions of characteristics of filter media, filter assemblies, test methods, and test materials. Inevitably, some terms have been applied loosely, so that the same term may have different meaning to different people, or in different frames of reference. Recognizing the need for clearly defined terms, which can have only one meaning for all persons in all circumstances, so that documents dealing with standard methods of evaluation of filters will have only one interpretation, the Filter Test methods Subcommittee of the SAE Engine Committee has compiled this Glossary of related terms. No attempt has been made to produce an all-inclusive document, containing definitions of all terms related to all types of fluid filters. Instead, the Glossary is confined to the terms likely to be encountered in relation to filters for lubricating oil and fuels. At the same time, we have recognized that some terms are common to all types of fluid filters, and have been careful to avoid conflict with the definitions published by other standardizing groups. If not identical, the definitions of these terms are at least worded to convey an identical meaning, hopefully in fewer, simpler or more precise words. We hope that this effort will be effective in helping to eliminate the ambiguities which have resulted from imprecise use of terminology and filtration. This Glossary is referenced in the SAE filter test methods documents. Terms used in those documents are intended to have the definitions shown by this Glossary, and no other. As new terms and their definitions become associated with the science of filtration and are relevant to the documents prepared by this subcommittee, revisions to the Glossary will be made, either by issuance of addenda or by revision and republication of the entire document.