I always thought that the phrase “First Lady” meant, by definition, the wife of the head of state; in particular, in the US, that it specifically meant the wife of the US President.<\/p>\n
But during a visit to the Vermont Marble Museum a couple months ago, in a hall of busts of Presidents, I saw an explanatory card that mentioned that during Buchanan's Presidency, since he was unmarried, his niece Harriet Lane was the First Lady.<\/p>\n
I couldn't figure out what that meant, since again I thought the definition of the term was “President's wife.”<\/p>\n
But it turns out that the term has, at least sometimes, more generally been used to mean (among other things) “hostess of the White House<\/a>”; and Ms. Lane is not the only unmarried woman to have served in that office.<\/p>\n In particular, the bit of that Wikipedia article that I find most surprising is the notion that Chelsea Clinton served as “Acting First Lady” during the two-week period between Hillary Clinton's swearing-in as Senator and Bill Clinton's leaving office as President.<\/p>\n But that's a contentious usage; the talk page<\/a> for that article makes clear that some people vehemently disagree with it.<\/p>\n And nowhere else on the web is the phrase “Acting First Lady” applied to Chelsea Clinton. (Except other pages that quote the Wikipedia article; you can filter them out of a Google search by looking for pages that don't contain the unusual phrase “during the fortnight”.)<\/p>\n