| Abbreviation | Definition |
|---|---|
| WF | Wallis and Futuna Islands |
| WFM | Waste-Free Mail |
| WHM | Work Hour Management |
| WKG | Working |
| WS | Samoa |
| WSPO | Wigmore Street Post Office |
| YE | Yemen |
| YT | Mayotte |
| YT | Yukon Territory |
| YU | Yugoslavia |
| ZA | South Africa |
| ZC | Zip Code |
| ZCTAs | ZIP Code Tabulation Areas |
| ZIP | Zone Improvement Plan |
| ZM | Zambia |
| ZMT | ZIP (Zoning Improvement Plan) Mail Translator |
| ZR | Zaire |
| ZW | Zimbabwe |