Where terms such as "about" or "approximately" are applied to a particular value (e.g. "about 200°C" or "approximately 200°C") or to a range (e.g. "about x to approximately y"), the value or range is interpreted as being as accurate as the method used to measure it. If no error margins are specified in the application, the same principles described in G‑VI, 8.1 apply, i.e. the expression "about 200°C" is interpreted as having the same round-off as "200°C". If error margins are specified in the application, they must be used in the claims in place of the expression containing "about" or similar terms.
When terms such as "substantially" or "approximately" are applied to qualify a structural unit of an apparatus (e.g. "a tray plate with a substantially circular circumference" or "a tray plate with an approximately curved base"), the expression containing the term "substantially" or "approximately" will be interpreted as a technical feature being produced within the technical tolerance of the method used to manufacture it (e.g. cutting a metal is much more accurate than cutting a plastic; or cutting with a CNC machine is more accurate than cutting by hand) unless the application suggests otherwise. In other words, in the absence of any indication to the contrary in the application, the expression "a tray plate with a substantially circular circumference" is interpreted as claiming the same technical feature as "a tray plate with a circular circumference"; in turn both expressions are considered as claiming any tray whose base the skilled person in the manufacturing field would consider as being circular.
The same applies when the expression containing "substantially" or "approximately" implies that a certain effect or result can be obtained within a certain tolerance and the skilled person knows how to obtain that tolerance. For example, "a substantially vertical seat back" is interpreted as allowing for a certain +/- variation around 90° where the skilled person can recognise that a functionality for supporting the sitting person's back is present.