A franc is a type of money used in several countries, most famously France until 2002, when it switched to the euro.

For centuries, if you visited Paris and wanted to buy a baguette or visit the Eiffel Tower, you'd pay in francs. French novels, movies, and history books often mention prices in francs: 20 francs for a meal, 100 francs for a train ticket.

Switzerland still uses the Swiss franc today, which is known for being extremely stable and valuable. Other countries like Belgium and Luxembourg once used francs too. Several African nations that were formerly French colonies also use currencies called francs, though these work differently from the original French franc.

When you read older books set in France, seeing prices in francs gives you a glimpse into history, like finding an old coin in your grandmother's drawer and imagining all the hands it passed through and all the things it bought over the decades.