This International Standard defines basic terms relating to ophthalmic optics, specifically to semi-finished spectacle lens blanks, finished spectacle lenses and fitting purposes. Terms relating to processes and material for fabrication and surface treatment (other than some specific terms relating to coatings, which are defined in Clause 16) and terms relating to defects in materials and after optical processing are given in ISO 9802. NOTE 1 At the time of publication, definitions quoted and acknowledged as being sourced from other International Standards are identical to those in the referenced editions of these documents (see Clause 2 and Bibliography, respectively). If, due to future revision of these International Standards, there should be disagreement between definitions in these International Standards and those in ISO 13666, then the definitions in the latest versions of the referenced documents take precedence. NOTE 2 In addition to terms and definitions used in the three official ISO languages (English, French and Russian), this International Standard gives the equivalent terms and definitions in the German language; these are published under the responsibility of the member body for Germany (DIN). However, only the terms and definitions given in the official languages can be considered as ISO terms and definitions.