1. When coding a diagnostic statement, identifies the condition, disease, or injury word(s) to look up in the alphabetical index of the International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) code book. 2. Alphabetical major headings printed in boldface that appear in the “Index,” which is the last section of the annually published Current Procedural Terminology code book. These main terms relate to procedures, services, organs, other anatomical sites, conditions, synonyms, eponyms, and abbreviations.