The common denominator of liberalism is the core liberal philosophy of universal individual rights & liberties, consent of the governed (governments exist for the people who have a right to change & replace them, & authority is legitimate only when it protects those liberties), political & legal equality.
US modern liberalism primarily refers to social liberalism & progressivism.
Liberalism elsewhere often refers to classical liberalism which more closely corresponds to US libertarianism.
Colloquially, liberalism is used differently, in its primary use in different countries. In the United States the general term liberalism almost always refers to modern liberalism. There are some parties in Europe which nominally appeal to social liberalism, with the Beveridge Group faction within the Liberal Democrats, the Danish Social Liberal Party, the Democratic Movement, and the Italian Republican Party. One of the greatest contrasts is between the usage in the United States and usage in Europe and Latin America. According to Arthur M. Schlesinger Jr. (writing in 1956), “[l]iberalism in the American usage has little in common with the word as used in the politics of any European country, save possibly Britain.” In Europe, liberalism usually means what is sometimes called classical liberalism, a commitment to limited government, laissez-faire economics. This classical liberalism sometimes more closely corresponds to the American definition of libertarianism, although some distinguish between classical liberalism and libertarianism.
Not all the parties using the “Liberal” or “Freedom” labels are actually liberal. Moreover, some parties, such as the Freedom Party of Austria, were originally liberal, but have since tilted toward a populist direction and abandoned most of the tenets of liberalism. Finally, some parties, such as the United States Republican Party, Australia’s Liberal Party or Norway’s Progress Party are liberal mainly from an economic point of view rather than a social point of view (see economic liberalism, libertarianism and right-libertarianism).
The common denominator of liberalism is the core liberal philosophy of universal individual rights & liberties, consent of the governed (governments exist for the people who have a right to change & replace them, & authority is legitimate only when it protects those liberties), political & legal equality. US modern liberalism primarily refers to social liberalism & progressivism. Liberalism elsewhere often refers to classical liberalism which more closely corresponds to US libertarianism.
American versus European usage of liberalism
Liberalism worldwide