Une énigme de Fort Boyard à résoudre

What does “un grain de beauté” mean in French?

Un grain is a single small particle, but French also uses it to measure things you cannot see. Un grain de folie is a welcome touch of madness, un grain de sable is the tiny thing that jams a plan, and un grain de beauté — literally “a grain of beauty” — is the ordinary word for a mole on your skin. One noun, four everyday images.

A Fort Boyard riddle strings these senses together: madness, pepper, beauty, and sand that can disrupt everything. The answer is le grain. The idiom extends naturally: un grain de sable dans l’engrenage — literally a grain of sand in the gears — is the tiny thing that jams a whole plan.