The northern part is called Saint-Martin[?] (the French term; note the dash); it is part of Guadeloupe, which is part of France.
The southern part is called Sint Maarten and is part of the Netherlands Antilles.
Although in an English text the dash could serve as distinction between the northern part and the whole island, to avoid confusion the former is commonly indicated as 'Saint-Martin (Guad.)'.
wikipedia.org dumped 2003-03-17 with terodump