Definition

1. Noun:
   • A law, practice, or institution that is no longer observed or effective: "dead letter" refers to something that has formally not been repealed but is completely ignored and no longer enforced in practice.
   • Mail that is undeliverable and cannot be returned to the sender: "dead letter" also refers to a piece of postal mail that cannot be delivered to its intended recipient and is also unreturnable, often ending up in a special office.

Usage Examples

• Noun (Obsolete rule):
  • That old regulation about formal dress is a dead letter; nobody follows it anymore.
  • The treaty became a dead letter after the war.
• Noun (Undeliverable mail):
  • The address was so illegible that the post office had to treat it as a dead letter.
  • The dead letter office handles mail that can neither be delivered nor returned.

Advanced Usage

• "to be a dead letter": to be a rule or agreement that is completely ignored.
  • Without enforcement, the new policy will quickly become a dead letter.
• "dead letter office": the postal department where undeliverable mail is processed.
  • The package was lost for months before finally being found in the dead letter office.

Variants and Related Words

• Dead-letter law/rule (n): a specific law or rule that is a dead letter.
  • The city has many dead-letter laws from the last century.
• Moribund (adj): (of an institution, practice, or custom) in a state of decline or inactivity, similar in meaning to the first sense of "dead letter".
  • The tradition is now moribund.

Synonyms

• Obsolete: no longer produced or used; out of date.
• Defunct: no longer existing or functioning.
• Undeliverable mail: mail that cannot be delivered (for the postal sense).

Related Phrases

• A dead issue: a topic or problem that is no longer relevant or debated.
  • That political debate is now a dead issue.
• To fall into disuse: to stop being used, leading to a state of being a dead letter.
  • The custom fell into disuse and is now a dead letter.

Related Idioms

• Dead in the water: completely unable to function or make progress, sharing a sense of ineffectiveness with "dead letter".
  • After the scandal, the proposed bill was dead in the water.

Noun

1. mail that can neither be delivered nor returned
2. the state of something that has outlived its relevance