A commissioner is, in principle, a member of a commission or an individual who has been given a commission ( official charge or authority to do something ).
In practice, the title of commissioner has evolved to include a variety of senior officials, often sitting on a specific commission. In particular, 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.
There is some confusionbetween commissioners and commissaries, because other European languages use the same word for both. Therefore titles such as commissaire in French, Kommissar in German and comisario in Spanish can mean either commissioner or commissary in English, depending on the context.
A Commissioner within a modern state generally holds his or her office by virtue of a commission from the head of state or a council of elected representatives (or appointed by non-elected officials in the case of dictatorships).
Commissioners are the formal heads of the territories in Canada (those areas under the formal jurisdiction of the federal Crown-in-Council and without separate constitutional status of a province). Unlike the governor general or a lieutenant governor, commissioners are not viceregal representatives of the Canadian monarch ; rather, they are delegates of the federal Crown-in-Council and, under federal statutes governing the territories, act in accordance with written instructions from Cabinet or the minister responsible (currently the Minister of Aboriginal Affairs and Northern Development).