All applications will contain one or more "independent" claims directed to the essential features of the invention. Any such claim may be followed by one or more claims concerning "particular embodiments" of that invention. It is evident that any claim relating to a particular embodiment must effectively include also the essential features of the invention, and hence must include all the features of at least one independent claim. The term "particular embodiment" should be construed broadly as meaning any more specific disclosure of the invention than that set out in the independent claim or claims.

Any claim which includes all the features of any other claim is termed a "dependent claim". Such a claim must contain, if possible at the beginning, a reference to the other claim, all features of which it includes (see, however, III, 3.8 for claims in different categories). Since a dependent claim does not by itself define all the characterising features of the subject-matter which it claims, expressions such as "characterised in that" or "characterised by" are not necessary in such a claim but are nevertheless permissible. A claim defining further particulars of an invention may include all the features of another dependent claim and should then refer back to that claim. Also, in some cases, a dependent claim may define a particular feature or features which may appropriately be added to more than one previous claim (independent or dependent). It follows that there are several possibilities: a dependent claim may refer back to one or more independent claims, to one or more dependent claims, or to both independent and dependent claims.