Definitives.org

Glossary of philatelical terms

U.N.

Abbreviation for United Nations.

U.P.A.E.

Acronym for Union Postal de las Americas y España (Postal Union of the Americas and Spain).

U.P.U.

Universal Postal Union: organization born in 1863 to regulate international postal usages and rates.

UN

In english catalogues: abbreviation for unused.

UNCATALOGUED

Stamp known to exist, but not listed in the catalogue.

UNESCO

Acronym for United Nations Educational, Scientific and Cultural Organization.

UNIFICATO

Italian stamp catalogue. It covers Italian Area, Western Europe, U.S.A., Israel and some other European countries.

UNIQUE

Stamp of which only a piece is known.

UNISSUED

Stamp ready for use but not issued.

UNITED NATIONS

Stamps sold in United Nations buildings of New York, Geneva and Vienna. They have postal validity in all the world.

USED

Stamp regularly used for sending a letter or for some postale service. Usually it is cancelled and does not have any gum on its back side.