doubler

One of French's most overloaded verbs: to double a quantity, to overtake a car on the road, to dub a film into another language, and to line a garment — four common, distinct meanings sharing little beyond the idea of adding a second layer.

• Les prix ont doublé en dix ans. — Prices have doubled in ten years.
• Il a doublé le camion dans un virage dangereux. — He overtook the truck on a dangerous bend.
• Ce film a été doublé en français. — This film was dubbed into French.

Learners often assume "to double" covers every sense, but doubler une voiture (to overtake) has nothing to do with doubling — it's one of the most common false-friend traps with this verb, since English "double" never means "pass."

• expression Doubler la mise — A gambling-derived idiom for raising one's stake or redoubling an effort or investment — mise being the money wagered — now standard in everyday and business French for intensifying commitment to something.