Adhesive: In actuality, what a stamp is: a piece of paper which, by way of its gummed or pressure-sensitive back, pays for postage when applied to a piece of mail. With revenue stamps, the adhesive pays some kind of tax.
Airmail Stamps: Postage stamps used to pay the airmail postage rates. The U.S. stopped issuing airmails stamps in the 1970s when all mail began to be sent by air.
Approvals: Priced selections of stamps sent to collectors by dealers. Collectors pick what they want to buy, and return the selection to the dealer with payment.
Arrow: On many sheets of stamps, small arrow markings appear in the sheet margin. This was done to aid in the perforation process.
As Is: A term usually used by auctions to denote that a stamp is offered for sale without any guarantees.
Authentication Mark: A tiny mark that appears on many older and rare stamps. It denotes that an expert has examined and approved the stamp’s authenticity.
Backstamp: Postmark applied to the reverse of a cover (see below for "Covers") to indicate transit or receipt of mail. Oval backstamps are also used on registered mail.
Block: An unsevered even-numbered group of stamps; i.e., block of four, six, 12, etc.
Bogus: A fictitious stamp-like label created solely for sale to collectors. Such "bogus stamps" are not good for postage.
Cancel, Cancellation: A marking, usually a handstamp or postmark, that indicates a stamp has been used.
Catalogue: Comprehensive listing of postage and revenue stamps, including current price valuations and illustrations.
Catalogue Value: The value of a stamp given by a stamp catalogue (i.e., Stanley Gibbons catalogue value, etc.). These valuations are not necessarily the prices at which the stamps can be purchased. Often, depending on condition, stamps can be purchased below catalogue value (or above, if the condition of the stamp/s warrant same).
Centering: The relative position of a stamp’s design in relation to the margins surrounding it. Centering is a very important consideration in determining a stamp’s value.
Classic Stamp/Issues: An early issue, with connotation of rarity.
Coil: Stamps prepared in rolls (of from 100 to 1,000) for use in vending machines.
Commemorative: A stamp issued to honour some person, place or event.
Condition: The overall state of a stamp or cover as it relates to everything from condition of the gum (present or absent), centering, presence or absence of damage to a stamp/cover, etc.
Counterfeit: Any stamp or cover or cancellation created for the purposes of deception.
Cover: An envelope or piece of postal stationery (a postcard would also fall into this category)---and usually one that has gone through the postal service. In earlier days (19th century), a cover would also refer to a folded letter that had gone through the mails.
Crease: Some kind of fold that indicates a weaking of the paper on a stamp or cover.
Cylinder: A printing plate used on a modern rotary printing press.
Definitive: A stamp issued for an indefinite period to pay a particular rate of postage. Also called "regular issues".
Denomination: The face value of a stamp.
Entire: An intact piece of postal stationery (i.e., envelopes on which the stamp has been printed).
Essay: Artwork of a proposed design for a stamp or piece of postal stationery. An essay must, in fact, be different in some way from the actual design of the issued stamp or stationery.
Expertisation: The examination of a philatelic item by an acknowledged expert in order to see if the item is genuine. This generally means an expertising body such as the American Philatelic Expertizing Service.
Face Value: The value of a stamp as noted on its face.
Fake: Stamp or cover that has been altered in order to raise its value or appeal to a collector.
First Day Cover: An envelope bearing a stamp (and official first day of issue postmark) which has been cancelled on the first day the stamp was issued to the public.
Forgery: A fraudulent reproduction of a postage stamp or cover.
Frame: The outside area of a stamp’s design.
Freak: An abnormal stamp that has some kind of printing flaw - it could be anything from overinking to perforation mistakes.
Grill: A waffle iron type of pattern impressed into some mid-19th century U.S. stamps to prevent such stamps from being washed and reused after their original use on mail.
Gum: The substance applied to the reverse of stamps to help them adhere to a mailing item.
Gutter: The selvedge or selvage (US), with or without plate numbers or controls numbers/letters between the panes of a sheet of stamps.
Handstamp: Some form of cancellation or postal marking.
Hinge: A tiny piece of glassine-like paper, gummed, folded and then used to mount stamps into an album.
Imperforate: Stamps without perforations or separation device between then on a sheet.
Invert: A term used for stamps printed in two or more colors and which has the active area of one of the colors printed upside down. The most famous such invert is the U.S. 24-cent inverted "Jenny" airmail stamp of 1918.
Line pair: A line printed between a pair of coil stamps. Appears because of the guideline that is printed between panes on a sheet of stamps.
Lithography: Flat surface printing with a design area that is ink-receptive. The area that is not to print is ink-repellant.
Margin: The selvedge surrounding the stamps on a sheet.
Meter Stamp: Government permit of various face value and printed by machine on a piece of adhesive paper (or on the actual envelope) to indicate postage paid. Invented by the Pitney-Bowes company in the early 1900s.
Miniature Sheet (MS) or Souvenir Sheet (SS): A smaller than normal sheetlet of stamps issued only in that form or in addition to the normal full panes of stamps.
Mint: A stamp in the same condition as when it was issued and purchased at the post office. Original gum is on the reverse and the stamp has never been hinged into an album.
MNH: Mint stamp (Never Hinged). Often referred to as NH in US stamp collecting.
Mounts: Vinyl or plastic holders, clear on the front and with gum on the back. Stamps and philatelic items are placed inside the mount and then mounted into an album.
Multicolour: More than two colours.
Multiple: An unseparated group of stamps (two or more).
Official: Stamp or stationery used to pay postage by a government agency.
Offset Printing: A printing process that transfers an inked image from a plate to a roller, the roller then applying the ink to the paper.
On Paper: Stamps, usually used, which have been used on mail and still adhere to all or part of that original piece of mail.
OG/Original Gum: The gummed surface on a stamp is the actual gum that was originally applied to that stamp.
Overprint: Any printing over the original design of a stamp. For instance, an overprint that upgrades or changes the value of a stamp.
Pair: Two unseparated stamps.
Pane: The unit into which a full sheet of stamps is divided before it is sold at a post office. Many U.S. stamps were printed in sheets of 400 and broken down into four panes of 100 stamps each before sale.
Penny Black: The world’s first postage stamp, the one-penny stamp issued by Great Britain in May 1840.
Perfins: Stamps punched with "perforated initials" or other designs and used generally by commercial firms in order to deter theft.
Perforation: The punching out of holes between stamps in order to aid in their separation. There are various kinds and sizes or perforations which are measured by a perforation gauge. Often, a particular size of perforation can differ on stamps that look very much alike. Different valuations can be the result.
Perforation Gauge: A metal, plastic or cardboard instrument used (easily) to measure the size of perforations (see above).
Philately: The collection and study of postage stamps and related items.
Photogravure: Modern printing process where stamps are printed through the photographic plate making process and through the use of chemicals.
Plate: The printing unit placed on a press to print stamps.
Plate Block, or Plate Number Block: A block of stamps which includes the corner selvedge from the pane and bearing plate numbers from the printing process.
PNC: Plate number coil.
Postage Due: Stamps or markings that indicate an underpayment of postage.
Postal History: The study of postal markings, routes and rates of mail. And anything to do with the history of the mails.
Postmark: An official postal marking usually giving the date and origin or a piece of mail and is often part of the cancellation obliterating a stamp to prevent reuse.
Precancel: Stamp with a special cancellation or overprint and which was applied before the stamp is used on mail. This bypasses normal cancelling and saves much time when large numbers of mail are being used.
Proofs: Trial impressions from a die or printing plate that are made before the formal production of stamps. Such proofs are made to check defects in the plate work or design of the stamps.
Reprint: A stamp printed from its original plate after that stamp has ceased to be sold and postally used.
Revenues: Stamps usd for the prepayment of payment of various kinds of taxes.
Rouletting: The piercing of the paper between stamps (as opposed to perforations which are holes) that creates slits to aid in separating the stamps.
Selvedge/Selvage: The unprinted marginal area around the outer edges on a sheet or pane of stamps.
"Specimen": Stamp or stationery overprinted "Specimen" and distributed to member countries of the Universal Postal Union.
Tagging: The impregnation of phosphorescent dies into the paper used to print a stamp. When "read" by special Ultra Violet machines during mail processing, the phosphors determine the face value of the stamp(s) being used to pay postage.
Topical or Thematic: A stamp or piece of stationery showing a particular subject; i.e., horses, birds, plants, transport, sporting events such as the World Cup, etc.
Unused: An uncancelled stamp (as opposed to a mint stamp, see above), but one that has been hinged for mounting into an album. Such stamps can be either gummed or ungummed (the gum having been washed off).
Used: A stamp or stationery item that has been used for the purpose for which it was intended: usage on the mail. Such an item usually bears all or part of a cancel or obliteration device.
Variety: A variation from the standard form of a stamp. Varieties can include watermarks, different kinds of perforations, wrong colours or printing and production mistakes (overinking, missing colours, etc.)
Watermark: A machine-applied, deliberate thinning of paper during its manufacture, to produce a semi-transparent pattern or design of some kind.