This study is one of a series using consistent definitions of key concepts to support analysis of changes over time. The studies are designed to explore the process by which faculty members select and use the educational materials that they employ in their courses. The most common of these is the required textbook: faculty members typically select one or more books that all students are required to use throughout the duration of the course. Faculty also employ a wide range of other materials: some optional, others required for all students. In addition to examining the overall resource selection process, this study also explores the particular class of materials classified as open educational resources (OER). The 2017-2018 survey on teaching materials in U.S. higher education shows a steady growth in awareness of open educational resources (OER). Responses from over 4,000 faculty and department chairpersons paint a picture of steady improvement, with almost 50% of faculty now reporting OER awareness. [For "Opening the Textbook: Educational Resources in U.S. Higher Education, 2017," see ED582411.]