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Inventions. International Patent Classification

The Strasbourg Agreement concerning the International Patent Classification (1971), which entered into force on October 7, 1975, provides for a common Classification for patents for invention, inventors’ certificates on inventions, utility models.

International Patent Classification (hereinafter referred to as the IPC) is designed to enable an internationally uniform classification of documents. The person who classifies the document will allot the classification symbols, according to the IPC edition in force on the date of classification.

Principles of the classification

Patent documents may include two types of information:

  • invention information;
  • additional information.

For both categories of information will be applied the same rules for the allotment of classification symbols.

Invention information is technical information in the total disclosure of a patent document (for example, in the claims, description and drawings, where appropriate) that represent a contribution made by the invention to the state of the art.

Additional information is non-trivial technical information which does not in itself represent a contribution to the state of the art but might constitute itself information for the searcher.

Subject-matter of the invention

Inventions can have as subject-matter processes, products, equipment or materials (or the way they are used or applied).

Classification places corresponding to subject-matters of the invention

The classification ensures that any technical subject with which an invention is essentially concerned can be classified, as far as possible, as a whole and not by separate classification of constituent parts.

In turn, constituent parts of a technical subject of invention may also constitute invention information if they themselves represent a contribution to the state of the art, i.e. they represent novel and unobvious subject-matter. Invention information shall always be presented by classification symbols.

Additional information shall be represented by classification symbols, indexing codes or both. Thus, the classification includes all knowledge that can be regarded as relevant in the field of patents for invention and is divided into 8 sections.

Section Symbol: Each section is designated by one of the capital letters A through H.

Section Title: The section title is to be considered as a very broad indication of the contents of the section.

The eight sections are entitled as follows:

  • A. Human Necessities
  • B. Performing operations; Transporting
  • C. Chemistry; Metallurgy
  • D. Textiles; Paper
  • E. Fixed Construction
  • F. Mechanical Engineering; Lighting; Heating; Weapons; Blasting
  • G. Physics
  • H. Electricity

To understand the methodology of the procedure for correct and accurate classification of patent documents and more efficient use of the patent system as a means of information, use the “Guide to the International Patent Classification”, intended for users of industrial property system, especially applicants/patent owners, representatives in industrial property, AGEPI examiners and persons involved in search, both in research and development institutions and AGEPI, which is available electronically and on paper.

IPC Structure

For example, the classification index A61K 31/00 has the following structure:







1st level


2nd level


3rd level

Main group

4th level


More detailed classification level



However, the hierarchy among subgroups is determined by the number of dots preceding their titles, for example:

G01N 33/483 ... Physical analysis of biological material

33/487 ... of liquid biological material

33/49 ... blood

33/50 ... Chemical analysis of biological material, for example blood

For a better understanding of the principles and mode of classification of inventions we propose you to use the Guide to the international patent classification.

Clasificarea Internațională a BrevetelorInternational Patent Classification,

New edition of the International Patent Classification (in Russian).