The term CIRCULATE, AS LIBRARY BOOKS can be solved by the four letter word LEND. To LEND means to give something temporarily, usually with the expectation that it will be returned. In the context of library books, this means that a library patron can borrow a book from the library for a certain period of time, and then return it when they are finished. Circulating library books is an important part of library operations, as it allows patrons to access materials without having to purchase them.