Using the ILO Classification system, "s", "t", and/or "u" opacities predominate.
ILO | Köppen climate classification | British undergraduate degree classification | British Board of Film Classification | Points classification in the Vuelta a España | Mountains classification in the Giro d'Italia | Biological classification | Race (classification of human beings) | Dewey Decimal Classification | Bordeaux Wine Official Classification of 1855 | Stellar classification | Mathematics Subject Classification | Library of Congress Classification | Classification of discontinuities | Race (human classification) | Office of Film and Literature Classification | Classification of Champagne vineyards | Young rider classification in the Tour de France | Settlement classification in Mexico | Office of Film and Literature Classification (Australia) | Mountains classification in the Vuelta a España | Irish Film Classification Office | International Patent Classification | International Association of Classification Societies | Classification yard | Classification of demons | Australian Classification Board | young rider classification in the Tour de France | Universal Decimal Classification | Thibaudeau classification |
International Standard Classification of Occupations, an International Labour Organization (ILO) classification structure