Abbreviated (UDCL). A six-step colour naming system designed for use in specifying (i .e. , grading) the colour of diamonds. The UDCL features six levels of colour description, arranged from the least precise to the most precise: 1 = common colour name; 2 = colour variety; 3 = colour modifier(s); 4 =lightness; 5 = saturation; and 6 = numerical (CIELAB) colour notation (see chapter 7). In this system, the description of colour in a diamond takes into account the use of common colour names (e .g., cognac) ; recognizes the use of general colour names (e .g., yellowish orangish brown, medium-dark, moderate-strong) and separates them according to variety (dominant hue), modifier (secondary hue), lightness, and saturation; and provides a more precise method for denoting colour through the use of numerical colour notations (e.g., CIELAB). Any one of these levels of colour description (i.e., common names, general names, or numerical notations) are appropriate for describing the colour of a diamond because they are synonymous with each other; they merely represent different levels of precision . At the present time, most industry professionals (i .e., wholesale dealers and retail merchants) describe diamond colours with common colour names and/or general colour names, because these verbal descriptions are easy and they agree with a person ‘s normal idea of a certain colour. However, when more precision is required (e.g. , to explain the difference between two coloured diamonds that appear quite similar), one must resort to describing their individual colours (and colour difference) with numbers (i.e., colour notations derived from a specific colour order system such as CIE L*a*b*). (Hofer 1988, Nos 2 & 3; 1989, Nos 5 & 6; 1990, Nos 7 & 8)