European Union member states disagree on what vodka should be made of.
The EU's current legal definition of vodka says it can be made from any agricultural produce.
But some countries say that real vodka is made only from grain or potatoes.
The European Parliament has approved a compromise which says vodka made from more than just grain or potatoes can still be called "vodka" but the other ingredients must be clearly identified on the label.
What, in practice, is vodka made of?
Different countries make it in different ways. Wheat is most popular in Russia and Sweden, barley in Finland, rye and potato in Poland. It is also made from sugar beet molasses and fruit, including grapes, in some countries.
In principle a clear "white" spirit can be distilled from anything that ferments. It is reported that coal was used in communist Poland, but that efforts to use chickens were unsuccessful. A by-product of the wood-pulp industry was once used in Sweden.
Where does vodka come from?
The word "vodka" is derived from "voda", which means water in Russian and Polish. The use of vodka as a flavourless mixer in cocktails is a fashion which began in the US, and took off in Western Europe after World War II.
Who drinks it?
More and more of us. The UK's Gin and Vodka Association says vodka has overtaken whisky as the biggest-selling spirit in the UK. The vodka market is also growing rapidly in Germany and southern Europe, and is huge in the US.
It has a very large, but declining, share of the spirits market in Sweden and Poland.
Globally, vodka is worth $12bn annually. Some 4.5bn litres is produced each year, though more than half of that is drunk in Russia.
Who would be worst affected if drinks made from sugar beet or fruit were not counted as vodka?
One estimate doing the rounds says that two-thirds of EU production outside the Baltic region would be eliminated. About one-third of the UK's output would be in trouble, mainly supermarket own-label vodka and other budget brands made from sugar beet.
Southern European countries which make grape-based vodkas would also be disadvantaged.
What is the argument in favour of labelling ingredients, when vodka is made from anything other than grain or potatoes?
Some MEPs say that it is generally a good principle to label ingredients, because it lets consumers know what they are buying.
However, others say insisting on labelling some raw materials - sugar beet molasses and fruit - and not others, amounts to a form of protectionism, put forward by member states with a tradition of making vodka from grain and potatoes.
Do vodkas made from different raw materials taste different?
It depends on the method of distillation. Some vodkas are distilled in such a way that the flavour of the raw material completely disappears. But the tendency in Poland and the Nordic countries is to preserve some of the taste produced by the raw material.
It takes a very experienced vodka drinker, however, to identify the flavour of rye, wheat, potato etc.
How did the European Commission propose to define vodka in the original regulation?
Like this: "Vodka is a spirit drink produced from ethyl alcohol of agricultural origin."
Its proposed draft went on to say that vodka is "distilled and/or rectified so that the organoleptic characteristics of the raw materials used and by-products formed in fermentation are selectively reduced".
The minimum strength is 37.5%.
What does the European Parliament think?
Its environment committee proposed continuing to allow vodka to be made from any agricultural produce.
However, it said that the raw material of any vodka not made from grain, potato or molasses should be clearly labelled.
It also said that vodkas made from more than one ingredient should be labelled as "blended vodka".
What does the compromise text propose?
It adds sugar beet molasses to the list of raw materials that must be labelled.
On the other hand, it also removes a requirement that raw materials should be labelled in letters no less than two-thirds the size of the word "vodka".
So consumers could have to look quite hard at a vodka bottle to discover what its contents are made of.
The new spirit labelling rules also state that whisky cannot contain flavourings or sweeteners - a move welcomed by distillers of traditional "Scotch Whisky".
How long has vodka been around?
In Russia and Poland it has been around for hundreds of years. Smirnoff left Russia after the revolution and began production in the US after the end of prohibition. The company first made vodka in the UK in 1952.
The first spirits branded as vodka in Nordic countries went on sale in the 1970s.
Do people really drink it neat?
It is still drunk neat with dinner in Russia and some other parts of Eastern Europe: someone pronounces a toast and everyone downs their glass of vodka in one.
The same also happens at celebratory meals in Central and Northern Europe - at weddings for example - though there is an increasing tendency among the young to drink it with mixers and in cocktails, as in Western Europe and the US.