What are the different types of subject matter combinations in patent classification?

This page is an FAQ based on guidance from the Manual of Patent Examining Procedure. It is provided as guidance, with links to the ground truth sources. This is information only: it is not legal advice.

According to MPEP 903.02(b), there are several types of subject matter combinations in patent classification:

• Basic Subject Matter Combined with Feature for Some Additional Purpose: The MPEP states, “The added purpose is in excess of the scope of the subject matter for the class, as defined in the class definition; e.g., adding a sifter to a stone crusher which gives the added function of separating the crushed stone.”
• Basic Subject Matter Combined with Perfecting Feature: “Features may be added to the basic subject matter which do not change the character thereof, but do perfect it for its intended purpose; e.g., an overload release means tends to perfect a stonecrusher by providing means to stop it on overload and thus prevent ruining the machine.”
• Basic Subject Matter: “The combination of features necessary and essential to the fundamental character of the subject matter treated; e.g., a stonecrusher requires a minimum number of features as essential before it can function as such.”

Understanding these combinations is crucial for proper patent classification and searching.