In the commercial area, classification of chemicals is not as straightforward as in the scientific area. Depending on the perspective taken, different levels can be utilized - moving from segments consisting of individual chemical compounds to the other extreme of segments only defined by the end use of chemicals. In between, there are several other levels in which both perspectives are mixed to a certain degree. The different levels are discussed along with the issues arising from their often simultaneous use. In addition, guidelines are given on the suitability of different levels for specific areas of the chemical industry.