| Airmail Stamp | Stamp issued specifically to prepay postage for mail carried by air. |
| Approvals | Look before buying" opportunity where stamps are sent to a collector for examination. Approvals offer the collector a wide range of material to choose from and must be bought or returned to the dealer within a specified time. |
| Block | Four or more attached stamps forming a square or rectangle. |
| Booklet Panes | Small, specifically-printed sheets of stamps sold in a booklet format. |
| Cachet | Illustration or description on an envelope denoting the commemorative purpose for which it was mailed. |
| Cancellation | Any mark applied to a stamp to prevent its reuse. |
| Centering | The position of the design on a stamp. On perfectly centered stamps, the design is exactly in the middle. Coil Stamp Stamp produced in a roll for use in vending machines. Usually identified by a pair of straight edges on opposite sides. |
| Commemorative Stamp | Stamp issued specifically to honor a person, place or event; usually on sale for only a short period of time. |
| Commemorative Sheet | A small sheet of stamps bearing a commemorative inscription. |
| Cover | An envelope, postcard or any other wrapper used to mail correspondence. |
| Cut Square | The cut corner of a postal stationery item (envelope or postcard) bearing the imprinted stamp with ample margins. |
| Definitive | Stamp issued for ordinary postal use that remains on sale for an extended period of time. |
| 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. |
| Embossed Envelope | An envelope bearing a postage stamp with raised surface designs printed on the envelope itself. |
| Errors | Highly-collectible stamps because of something incorrect in their design or manufacture. |
| First Day Cover | Envelope or card postmarked on the affixed stamp's first day of use. |
| First Flight Cover | Envelope or card carried on the inaugural mail flight between two points. |
| Grill | 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. |
| Hinges | Small gummed, glassine strips used to affix stamps to album pages. |
| 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. |
| Mint Sheet | An entire sheet of stamps in original unused condition. |
| Official Stamp | Stamp valid solely for government agency use. |
| 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. |
| Philately | Technical name for stamp collecting. |
| Pictorial | Stamp that features a view such as a landscape or seascape, rather than a portrait, coat of arms or other symbolic design. |
| 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. |
| Rouletting | The use of slits or cuts between stamps to facilitate separation. |
| Selvage | Unprinted paper around panes of stamps, sometimes called the margin. |
| Semi-Postal | Stamp from which all or part of the sales receipts go to charity or other causes. |
| Se-Tenant | Term describing adjoining stamps that differ from each other in design, denomination or some other aspect. |
| Surcharge | Overprint altering or establishing a stamp's face value. |
| Tab | Illustrated or descriptive label attached to a stamp. |
| Tongs | Metal tweezers used for safe and easy handling of stamps. |
| Topicals | A group of stamps with the same theme, such as space travel or Disney cartoons. |
| 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. |
| Watermark Detector | A method of safely determining the existence of a watermark by placing a stamp in a tray filled with special fluid. |

