ISO 9211 identifies surface treatments of components and substrates excluding ophthalmic optics (spectacles) by the application of optical coatings and gives a standard form for their specification. It defines the general characteristics and the test and measurement methods whenever necessary, but is not intended to define the process method. This part of ISO 9211 defines terms relevant to optical coatings. These terms are grouped in four classes: basic definitions, definition of coatings by function, definitions of common coating imperfections and other definitions.