The term administration, as used in the context of government, differs according to jurisdiction.
In American usage, the term refers to the executive branch under a specific president (or governor, mayor, or other local executive), for example: the "Obama administration.” It can also mean an executive branch agency headed by an administrator: these agencies tend to have a regulatory function as well as an administrative function. On occasion, people in the United States will use the term to refer to the time a given person was president, e.g. "they have been married since the Carter administration."
The term "administration" has been used to denote the executive branch in presidential systems of government.
Usage in Europe varies by country, but most typically the term 'administration' refers to managerial functions in general, which may include local governments, or the hierarchy of national and local government, that applies to a town or district. More specifically, it may refer to public administration, the business of administering public policy as determined by government. However, outside France and Romania, this usage of the word is uncommon.
For the American sense of the word, most countries (be they English-speaking or not) use the term government instead, referring to the “administration” of Tony Blair as the “Blair government”. This is also true of the non-European members of the Commonwealth of Nations. An older, chiefly Commonwealth usage, is the term “ministry”, as in Blair Ministry, which is still in official and academic use in Britain, Australia and Canada to refer the terms of prime ministers.