Master (Peerage of Scotland)
The heir apparent or heir presumptive to a Scottish peerage is known as a Master, or a Mistress if the heir is female. The heir's style is "The Master of [Peerage]" or "The Mistress of [Peerage]". If the master is an heir apparent, and the peerage has a subsidiary title that could be used as a courtesy title, then the styling of Master is usually forgone. However, if the person is an heir presumptive, or if the peerage has no subsidiary title, then Master/Mistress is a common styling. However, because the word Mistress is  quite archaic, many women choose not to use the style Mistress and instead use the regular styling, e.g. Lady Mary Smith or The Honourable Mary Smith. Although regarded today as a form of courtesy title, the Mastership is a dignity in its own right, and originally conferred rights of attendance in the Parliament of Scotland. As noblemen, Masters were ineligible for election to the House of Commons of Great Britain for Scottish constituencies. Masters whose elections were declared void on this basis included four elected in the 1708 British general election, who each briefly attended parliament: Lord Johnstone (the Master  of Annandale), Lord Haddo (the Master of Aberdeen), Lord Strathnaver (the Master of Sutherland) and the John, Master of Sinclair (never recognized as Lord Sinclair). Lord Elcho was excluded from Parliament in 1787 on the grounds that he had become the Master of Wemyss, though in fact the peerage was under forfeiture.