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 (3-4)) 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.