To do this, Open­Type in­cludes lay­out fea­tures—com­monly known as Open­Type fea­tures—that al­low fonts to spec­ify al­ter­nate let­ter­forms, and rules for how they should be in­serted into the text. These fea­tures are manda­tory for han­dling lan­guages like Ara­bic and Urdu.