The system has been nearly globally adopted. Burma, Liberia and the United States have not adopted SI units as their official system of weights and measures. The U.S. does not commonly use metric units outside of science, medicine, and the government,[4] but has officially defined its customary units in terms of SI units. The United Kingdom has officially adopted a partial metrication policy, with no intention of replacing imperial units entirely. Canada has adopted it for most purposes but imperial units are still legally permitted and remain in common use throughout a few sectors of Canadian society, particularly in the buildings, trades and railways sectors.