In T 378/02
, claim 1 contained the terms "a smooth impermeable surface". The appellants argued that the definition of the surface was ambiguous, because "smooth" was a relative term. The board recalled that, while relative terms constituted a potentially unclear element due to their characteristic to change their meaning according to the context, they nevertheless could be considered as clear and their use in a patent therefore allowed, if their meaning was clear in the context of the whole disclosure (see e.g. T 860/93
, OJ 1995, 47, for "water-soluble", T 860/95
for "a long period of time", T 649/97
for "transparent", T 1041/98
for "thin plate", T 193/01
for "thin film composite"). In contrast, in decision T 728/98
the term "substantially pure" was considered unclear per se and in the light of the description. The board considered that, in the context of the disclosure of the patent in suit as a whole, the term "smooth" represented a clear definition.