Nominal property, property of a phenomenon, body, or substance,where the property has no magnitude (VIM 1.30).
The current definition of quantity clearly excludes properties that, although carrying valuable information, can only be described in words. Examples include the colour of a spot test in chemistry (e.g. Schiff test for aldehydes), and molecular sequences (e.g. of amino acids in a polypeptide, of nucleotides in a DNA fragment). Such important properties, that have no magnitude, are however acknowledged in VIM3 and described with the term nominal property. In analytical chemistry the term qualitative analysis is often used to describe the examination of nominal properties.
It is possible to measure a quantity (see the definition of measurement), whereas obtaining information about a nominal property is not a measurement. The term examination is appropriate . However, in ISO 15189 the term ‘examination’ is used for both the determination of nominal property values and for measurement.
ref: Terminology in Analytica Measurement Introduction to VIM 3
