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Claims frequently contain terms that are imprecise. This does not give rise to an objection of lack of clarity if it is possible to ascertain whether an act would fall within the scope of the claim. This is a practical determination, rather than a strictly literal exercise, and it is acceptable if there is minor uncertainty at the edges of a claim.  Thus:

"The court will give little weight to puzzles which may arise 'at the edge of the claim' if those puzzles would not , as a practical matter, cause difficulty for the skilled addressee or manufacturer wishing to satisfy himself that what he proposes to do will not infringe that patent."

Glaverbel SA v British Coal Corp [1994] RPC 443 at 495.  

Examination Practice

Only clarity matters that affect the overall scope of the monopoly should be raised. In general, objections will be restricted to situations where the imprecise terms relate to the inventive concept and the terms would not be understood by the person skilled in the art. Consequently, terms such as "about", "substantially", "approximately", "essentially", "particularly", "preferably", or "for instance" should only be objected to if they cause the ambit of the claim to become uncertain. Similarly, the term "and/or" is not objectionable unless either the "and" or "or" form has uncertain scope.

See also “Substantially” and “About”.

Case Law

In Monsanto Company v Commissioner of Patents (1974) 48 ALJR 59 , the term "substantial effect as a cooling medium" was used. It was found that although "substantial" is imprecise, in the facts of the case it did not cause any ambiguity. The judge found that those skilled in the art would have little difficulty in determining when there was a "substantial" effect.

Similarly, in Catnic Components Ltd v Hill & Smith Ltd [1982] RPC 183, the term ‘vertical’ in the context used in the specification did not mean exactly vertical.

By way of contrast, in Shell Internationale Research Maatschappij N.V. v Monsanto Co (1968) AOJP 2397 the term "predetermined" was used to qualify "amount". It was found that the specification provided no means for determining the amount and there was no evidence that it could be determined as a matter of routine. In this circumstance the claim was not clear.

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