ROME — Italy’s political convulsions have raised new fears about the future of the euro, the single currency of the European Union that was introduced 16 years ago.

The possibility, however remote, that a populist Italian government would renounce the euro and revive the lira currency has unnerved many bankers and investors. Stocks tumbled on Tuesday on the fears, and the euro fell against the dollar to its weakest level in six months.

Here is a look at why the fears could escalate into a major crisis, and what it could mean for Italy, the euro, Europe and the world.

Why is everyone talking about the euro in Italy?

Italians have actually been talking about the euro since they began using it in 2002. For years, they have complained that their spending power has diminished under the euro. But the populists who did well in the election also say euro membership has subverted Italy’s sovereignty — an increasingly resonant theme in the country.