3.1 This terminology standard contains definitions of appearance terms applicable to the work of many ASTM technical committees. Its use by committees other than Committee E12 on Color and Appearance, and its citation in the standards of such committees, is encouraged.

3.2 In this terminology standard, definitions of terms used in other ASTM standards are indicated by placing the designation of that standard in parentheses at the end of the definition. Definitions used by other organizations (see Refs ( 5 7 ) ) are indicated similarly by placing in parentheses at the end of the definition the acronym of the organization, occasionally with the date of its terminology standard quoted. In either case, a superscript letter may be used to indicate the degree of correspondence between the definition given herein and that in the citation. Superscript A indicates that the two are identical; B that the given definition is a modification of that cited, with little difference in essential meaning; and C that the two differ substantially.

3.3 A further parenthetical inclusion at the end of the definition gives the revision, if after 1981, in which the definition was added to this terminology standard or last revised.

3.4 Where appropriate, symbols or acronyms are listed for terms in this terminology standard. Since usage varies, these listings should be considered as recommendations, not as mandatory. If a different symbol or acronym is used in another ASTM standard, this should be indicated in that standard.

3.5 In the 1990 edition of this terminology standard, a great many terms were relocated to conform to the recommendation of the Form and Style for ASTM Standards , (Blue Book) that listings be in spoken word order. In general, there are no cross-references between the old and new listings, except where a special function is served. An example of such a special function is to list all terms relating to a given basic quantity, for example, all terms defining various sorts of angles.

3.6 This terminology standard adopts the following usage of certain word endings. The ending ion denotes a process, as in reflection ; ance denotes a property of a specimen, as in reflectance ; and ity denotes a property of the kind of material of which the specimen is composed, as in reflectivity . Exceptions exist, as in the common use of illumination and radiation to refer to quantities as well as processes.

1.1 This terminology standard defines terms used in the description of appearance, including but not limited to color, gloss, opacity, scattering, texture, and visibility of both materials (ordinary, fluorescent, retroreflective) and light sources (including visual display units).

1.2 It is the policy of ASTM Committee E12 on Color and Appearance that this terminology standard include important terms and definitions explicit to the scope, whether or not the terms are currently used in an ASTM standard. Terms that are in common use and appear in common-language dictionaries (see Refs ( 1 4 ) ² ) are generally not included, except when the dictionaries show multiple definitions and it seems desirable to indicate the definitions recommended for E12 standards.

1.3 The usage of terms describing appearance varies considerably. In some cases, different usage of a term in different fields has been noted.