dead letter

• Une loi, une règle ou un accord qui reste officiellement en vigueur mais qui n'est plus appliqué ni respecté ; désigne également une lettre qui ne peut pas être distribuée par le service postal en raison d'une adresse incorrecte ou manquante.

A law, rule, or agreement that remains officially in effect but is no longer enforced or followed; also refers to a letter that cannot be delivered by the postal service due to an incorrect or missing address.

1. Unenforced law or ruleC1formal

   A law, regulation, or agreement that remains officially in effect but is no longer applied or enforced.

   lettre morte

   • The old prohibition law is now a dead letter.
   • Many outdated regulations have become dead letters in modern society.
   • The treaty was signed but quickly became a dead letter.

2. Undeliverable mailB2formal

   A piece of mail that cannot be delivered to the intended recipient or returned to the sender.

   lettre morte

   • The post office has a special department for handling dead letters.
   • This letter was returned as a dead letter because the address was wrong.
   • Dead letters are eventually destroyed if unclaimed.