All of the utility classes (i.e., classes devoted to technology), and the plant class have definitions. All design classes will eventually have definitions.
Definitions state the subject matter of the classes and subclasses in much more detail than it is possible to state in the brief class and subclass titles. A study of the definitions is essential to determine the proper classification of subject matter within the U.S. Patent Classification System (USPC).
All classes and subclasses (class definitions) in the USPC are available online to USPTO personnel from the Classification Home Page under the heading Search Classification Data. The Classification Home Page (http://ptoweb:8081/) is accessible from the desktop via the Patent Examiner’s Toolkit. The class definitions are archived in portable document formats (PDFs) to CD-ROM every June and December.
It should be noted that classification orders frequently affect existing definitions. Personal sets of definitions used by examiners should be periodically revised to reflect these changes. Classification Orders are available online to USPTO personnel from the Classification Home Page under the heading Classification Reports. The Classification Home Page is accessible from the desktop via the Patent Examiner’s Toolkit.