Materials that can be removed from the premises, or checked-out, may circulate. Reference books, or items in special collections, do not circulate.

This is what it's called when a book is checked out. Most of the library material which is checked out can be taken from the building, but some such as reserve material must be used in the library. Other items may not circulate at all. Items which often do not circulate are reference books, periodicals, and expensive or rare items.

Materials which can be charged are said to circulate.

To lend for use outside of the library.

To sign out materials from the library for a stated period of time.

books that circulate may be borrowed for use outside the library.

Materials that can be borrowed form the library circulate. Books identified as "reference" or "building only" are noncirculating and cannot be borrowed.

means a book can be borrowed or checked out.