In practice, the title of commissioner has evolved to include a variety of senior officials, often sitting on a specific commission. In particular, the commissioner frequently refers to senior police or government officials. A High Commissioner is equivalent to an ambassador, originally between the United Kingdom and the Dominions and now between all Commonwealth states, whether Commonwealth realms, republics or countries having a monarch other than that of the realms. The title is sometimes given to senior officials in the private sector; for instance, many North American sports leagues.