Particular attention is required whenever the word Where terms such as "about" or similar terms such asor "approximately" or "substantially" are used. Such a word may be applied, for example, to a particular value (e.g. "about 200 °C" or "approximately 200 °C"), or to a range (e.g. "about x to about approximately y") or, 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 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). In other words 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.
In each case, the examiner should use his judgment as to whether the meaning is sufficiently clear in the context of the application read as a whole, and having regard to the meaning a particular technical term qualified by such a word usually has in the field concerned. If such words mean that a certain effect or result can be obtained within a certain tolerance and the skilled person knows how to obtain the tolerance, then the use of such words may be acceptable.