Open Educational Resources (OER) are learning, teaching, and research materials in any format and medium that reside in the public domain or have an open license copyright that permits no-cost access, re-use, re-purpose, retention, redistribution, and adaptation by others.
Creative Commons adaptation of the UNESCO OER definition
ZTC = Zero Textbook Cost
Zero textbook cost means that students do not incur any costs for purchasing textbooks for the course. Instructors can use Open Educational Resources (OER); Open Access, Creative Commons, and public domain materials; along with resources owned or licensed by the Library.
Note: Zero-cost to the students does not mean zero cost to the institution. Library collections and subscription and other paid materials could be used to make the course ZTC.