This glossary provides a definition for each philatelic term used to describe the technical characteristics of postage stamps registered in the WADP Numbering System (WNS). Other elements relating to the WNS website are also provided.

Only the basic illustration of the stamp is registered in the system. A new entry is created if the size of the illustration varies by more than 10%. Small differences in color and design justify a new entry. 

However, stamps with different labels or tabs are not necessarily recorded separately if the stamps cannot be differentiated from each other once separated from the label or tab.

Since several terms are used to describe souvenir sheets, miniature sheets, or sheetlets, the WNS uses the standard term miniature sheet.

When a registered stamp is part of a souvenir or miniature sheet, a picture to the latter is accessible through a link on the page of each stamp of the miniature sheet. This link is clearly visible on the detailed information of each of the stamps concerned (see below: Format).

Each stamp is allocated to at least one theme from the WNS standard list, based on the subject matter portrayed on the stamp and/or the purpose for which the stamp was issued. 

In order to facilitate the stamp search based on its theme, one or more main themes are specified. These can be supplemented by a more detailed sub-theme.

The subject is entered based on the information provided by the issuing postal authority. This is supplemented with further information to facilitate the search using the keyword search tool.

The horizontal (width) and vertical (height) dimensions of the stamps are registered with an accuracy of +/- 0.5 mm and are measured from the inner edges of the perforations. 

Stamps are measured upon registration, and these measurements are used unless the issuing postal authority provides more accurate data.

The maximum width and height are retained for stamps with unusual shapes.

The stamp denomination (face value) is indicated using the ISO currency code of the issuing postal authority. 

Stamps without denomination are registered using the terminology of the issuing postal authority, e.g. Brev, 1st class, Europe, For Local Addresses Only (FLOA), etc.

The objective of the system is to provide sufficient technical information using standardized terminology to identify the stamp. 

Stamps printed on gummed paper form a sheet of stamps and the number of stamps in the sheet is specified, if provided by the issuing authority of the stamp.

When the stamps are in other formats, such as self-adhesive stamp, booklets or coils, this information appears as provided by the issuing authority. If the latter provides the different formats, additional links to the corresponding images are added.

Stamps presented in different formats are not recorded separately, unless they can be differentiated from each other by a difference, albeit slight, in size, perforations or color.

Since several terms are used to describe souvenir sheets, miniature sheets, or sheetlets, the WNS uses the standard term miniature sheet. The scanned image of the miniature sheet can be accessed through the hyperlink in front of the format (see above: miniature sheet).

When the issuing postal authority communicates information about the printer, it is entered into the system as provided.

The perforation data is indicated as vertical followed by horizontal measurements using the international scale of the number of perforations within 2 cm of the stamp measured to the nearest decimal place (e.g. 13.5 by 14 indicates that the horizontal edge of the stamp has 13.5 perforations within 2 cm of stamp and the vertical edge has 14 perforations within 2 cm of stamp).

Perforations are measured upon registration unless this information in provided by the Issuing Authority.

If the issuing postal authority that is a member of the WNS has provided the address of its website and/or e-shop, a link to the latter is embedded in each page of the stamp search and of the statistics, to encourage and facilitate purchases.

This section of the website provides an exhaustive list of WNS member countries or territories, indicating the number of stamps issued each year since they joined the WNS. 

A hyperlink shows the number of stamps issued in a specific year. These are displayed underneath and are preceded by links to the website and/or online store of the issuing postal authority (provided that the latter has provided the address).

A link to refine the search from the stamp search section (by month, theme and keyword) is embedded in the results.

A tab on the navigation bar provides direct access to the philatelic circulars of the International Bureau of the UPU.

The purpose of philatelic circulars is to denounce detected illegal issues and to inform the designated operators of UPU member countries on various topics, such as regulations, commemorative issues, and major worldwide philatelic events.