With regard to the clarity of claims, the European Patent Office presently accept that the terms in the claims have their normal meaning, either in the language in which the claims are written or in the technical field in which the word is commonly used. There remains, however, one area in which objections to the lack of clarity of the claims prove extremely dangerous. This is when terms have general usage in the art but have no agreed definition. This point was illustrated by the Technical Board of Appeal Decision No. T337/95 (Nihon Nohyaku). In this particular case, the invention related to a chemical formula in which one of the substituents was a "lower alkyl". The term "lower" is used extensively throughout the organic chemical art, referring to the number of carbon atoms in a group. However, there is no agreement in the art as to the exact number of carbon atoms which provide the maximum number in a "lower alkyl" group. Accordingly, the European Patent Office found that the term was vague, as commonly used in the art and, therefore, the claim lacked clarity.

It is vitally important, when drafting an Application to form the eventual basis of the European Patent Application, that all terms be defined, if there is any doubt as to their exact meaning.