This section defines some basic CLOS terminology. We refer the reader to [X3J93][Ste90] for additional details. The definitions given in this section are derived from an online copy of a draft standard for CLOS, Common Lisp Object System Specification, by Daniel G. Bobrow, Linda G. DeMichiel, Richard P. Gabriel, Sonya E. Keene, Gregor Kiczales, and David A. Moon.