A S THEY CLEARED their heads after Burns Night on January 25th, having celebrated their national poet with whisky and haggis, another hangover loomed for Scots in less than a week’s time. A majority of them rejected Brexit in the referendum of 2016, whereas a majority in the United Kingdom overall supported it. Scotland is now leaving the European Union against its will—prompting a renewed call for Scotland, in turn, to leave the UK .

Naturally, the case for independence plays up characteristics that differentiate Scotland from England. Among them is language, which diverges from the talk south of the border in two main ways. One is Gaelic, a Celtic language impenetrable to outsiders (it is related closely to Irish and Manx but only distantly to English), which, however, is spoken only by around 50,000 people, or about 1% of Scotland’s population. The bigger difference is Scots—though quite how different it is remains a matter of debate.

As soon as you cross over from England, syntax and pronunciation change sharply. While the dialects of northern England have much in common with each other, the break at the border is stark. Because of that, some observers think Scots is not a dialect of English but a distinct (if related) language. The pro-independence Scottish National Party affirms as much in its manifestos.

Pronunciation is not enough to make Scots a language, or the Geordie English spoken in the north-east of England would be one, too. But it also has its own vocabulary, which goes beyond the well-known “aye, bonnie lass” of films and television. Scots descends from Northumbrian, one of the dialects of Old English; standard southern English descends from a dialect farther south. Scots retained Old English words that southern English lost, such as “bannock”. It was more influenced by Norse, in words such as gate (street) and kirk (church). It also has words from Gaelic, not just loch and whisky but quaich (a kind of bowl)and sonse (good luck). It has its own Norman French borrowings, not shared with English, such as douce (sedate, sober).

Still, vocabulary does not make a language either. More fundamental still is grammar—and here, Scots stands out again. Its speakers say “I’m going to my bed” whereas Englishmen say simply “to bed”. “Dinnae” is a Scots version of “don’t”. “Div” commonly replaces the auxiliary verb “do”. There are past-tense forms such as jamp (jumped), and irregular plurals like een (eyes) and kye (cows).

The Scots Syntax Atlas, free online, also shows how Scots varies internally. If you find a long-missing item, you might say “there it is” in English. But while, in other contexts, “it is” contracts to “it’s”, you can’t say “there it’s!”—save in a belt of Scotland running roughly from Kilmarnock to Edinburgh. People in that belt are unlikely to say “so apparently himself is joining us for dinner,” while northern, highland and some island Scots do.

There is no consensus among professional linguists as to whether, in aggregate, these features make Scots a language, or merely a dialect. Geoffrey Pullum, an Englishman at the University of Edinburgh, leans towards language status. Despite his expertise (and living in Scotland), he “simply cannot understand two Scots-speaking workers when they are chatting with each other”. He emphasises those grammatical differences, as well as the long literary history of Scots.

David Adger, a Scot at Queen Mary University of London (and, like Mr Pullum, a specialist in syntax), is unconvinced. He studies Scots as one among many varieties of English. After all, people who speak it can vary their delivery from broad Scots to Scottish-accented standard English on a smooth continuum, depending on the circumstances.

This makes Scots and English different from, say, Danish and Norwegian. Speakers of those related tongues understand each other with few problems. But they are not in the habit of making transitions between the two—they speak one or the other. Politics is integral to the divide: Norwegian was consciously developed away from Danish as part of a push for independence.

As an old saying goes, “a language is a dialect with an army and a navy.” Recognition for Scots as a language may, ultimately, be clinched not by grammatical arguments but by political ones. In other words, proclaiming it to be a language to support Scottish independence may have little impact. But gain independence, and outsiders might take Scots seriously as a separate language, too.