| Airmail Stamp |
Stamp issued specifically to prepay postage for mail carried by air. |
| Block |
Four or more attached stamps forming a square or rectangle. |
| Booklet Panes |
Small, specifically-printed sheets of stamps sold in a booklet format. |
| Cancellation |
Any mark applied to a stamp to prevent its reuse. |
| Commemorative Stamp |
Stamp issued specifically to honor a person, place or event; usually on sale for only a short period of time. |
| Cover |
An envelope, postcard or any other wrapper used to mail correspondence. |
| Denomination |
The monetary value printed on a stamp. |
| Die |
The stamp design is engraved on this small flat piece of soft steel used to print the stamp. |
| Duck Stamp |
Issued annually since 1934, these U.S. duck hunting permits help finance the federal waterfowl program. |
| Errors |
Highly-collectible stamps because of something incorrect in their design or manufacture. |
| First Day Cover (FDC) |
Envelope or card postmarked on the affixed stamp's first day of use. |
| Grills (Grill on stamps) |
Series of small dots embossed on a stamp allowing ink from the postmark to sink in, thus preventing cleaning and reuse of the stamp. |
| Gum |
The coating of glue on the back of an unused stamp. |
| Hinged |
The gum has had a hinge applied to it. |
| Imperforate Stamp |
Stamp bearing straight edges on all four sides. |
| Invert |
Stamp with one part of its design upside down in relation to the rest of the stamp. |
| Mint |
Stamps in original unused condition, never canceled. |
| Never Hinged |
The stamp has never had a hinge applied to it. Never Hinged has an expanded meaning though, the gum must be in like new condition with no marks of any kind whether made by a hinge or by something else. |
| Overprint |
Any printing added to a stamp after the original printing was completed. |
| Pair |
Two unseparated stamps joined either vertically or horizontally. |
| Perforations |
Holes punched between stamps on a sheet to facilitate separation. |
| Perforation Gauge |
Device that measures the number of perforations on a stamp per two centimeters. |
| Plate Block |
Four or more attached stamps still fastened to the margin on which the number of the printing plate is inscribed. |
| Postal Stationery |
Envelopes, cards or other covers bearing imprinted or impressed stamps. |
| Postmark |
Marking on a postal item recording the date and/or origin of its transit through the mail system. |
| Precancel |
Stamp canceled by the post office before it is sold. |
| Revenue Stamp |
Any stamp that indicates payment of a tax or fee. |
| Unused |
A stamp with no cancellation or other sign of use. |
| Used |
A stamp that has been canceled. |
| Watermark |
Design or pattern in paper formed during the manufacturing process, valuable as a security precaution against forgery. |
