This glossary defines nearly 300 terms frequently encountered by stamp collectors and cover collectors. Precise definitions for many philatelic terms do not exist. One collector, dealer or society may define a term in one way, while others will use the term in a slightly different way.
For special uses of some of the terms listed and defined here, contact the appropriate specialist collector group.
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Cachet: In French, cachet means a stamp or a seal. On a cover, the cachet is an added design or text, often corresponding to the design of the postage stamp, the mailed journey of the cover, or some type of special event. Cachets appear on modern first-day covers, first-flight covers and special-event covers.
Canceled-to-order: "Stamps are ""canceled to order,'' usually in full sheets, by many governments. The cancels may be printed on the stamps at the same time that the stamp design is printed. A stamp with a cancel and with full gum is likely a CTO stamp, as CTOs do not see actual postal use. CTO stamps are sold to stamp dealers at large discounts from face value. Most catalogs say whether they price CTO stamps or genuinely used stamps."
Cancel: A marking intended to show a stamp has been used and is no longer valid as postage. Modern cancels usually include the name of the original mailing location or a nearby sorting facility and the date of mailing. Most cancellations also include a section of lines, bars, text or a design that prints upon the postage stamp to invalidate it. This part of a cancel is called the killer.
Cantonal stamps: Issues of Switzerland's cantons (states) used before the release of national stamps. The cantonal issues of Basel (1845), Geneva (1843-50) and Zurich (1843-50) are among the classics of philately.
Cape Triangles: Common name for the triangular Cape of Good Hope stamps of 1853-64, the first stamps printed in triangular format. The distinctive shape helped illiterate postal clerks distinguish letters originating in the colony from those from other colonies.
Catalog: A comprehensive book or similar compilation with descriptive information to help identify stamps. Many catalogs include values for the listed items. An auction catalog is published by the auction firm in advance of a planned sale to notify potential customers of the specific items that will be offered.
Catalog value: The value of a stamp as listed in a given catalog for the most common condition in which the stamp is collected. Some catalogs list stamps at a retail value, though actual dealer prices may vary substantially for reasons of condition, demand or other market factors. Most catalogs have a set minimum value for the most common stamps.
Censored mail: A cover bearing a handstamp or label indicating that the envelope has been opened and the contents inspected by a censor.
Centering: The relative position of the design of a stamp in relation to its margins. Assuming that a stamp is undamaged, centering is generally a very important factor in determining grade and value.
Certified mail: A service of most postal administrations that provides proof of mailing and delivery without indemnity for loss or damage.
Chalky paper: A chalk-surfaced paper for printing stamps. Any attempt to remove the cancel on a used chalky-paper stamp will also remove the design. Immersion of such stamps in water will cause the design to lift off. Touching chalky paper with silver will leave a discernible, pencil-like mark and is a means of distinguishing chalky paper.
Changeling: A stamp whose color has been changed-intentionally or unintentionally-by contact with a chemical or exposure to light.
Charity seals: Stamplike labels that are distributed by a charity. They have no postal validity, although they are often affixed to envelopes. United States Christmas seals are one example.
Charity stamp: see Semipostal.
Cinderella: A stamplike label that is not a postage stamp. Cinderellas include seals and bogus issues, as well as revenue stamps, local post issues and other similar items.
Classic: An early issue, often with a connotation of rarity, although classic stamps are not necessarily rare. A particularly scarce recent item may be referred to as a modern classic.
Cleaning (stamps): Soiled or stained stamps are sometimes cleaned with chemicals or by erasing. The cleaning is usually done to improve the appearance of a stamp. A cleaned stamp can also mean one from which a cancellation has been removed, making a used stamp appear unused.
Cliché: The individual unit consisting of the design of a single stamp, combined with others to make up the complete printing plate. Individual designs on modern one-piece printing plates are referred to as subjects.
Coil: Stamps processed in a long single row and prepared for sale in rolls, often for dispensing from stamp-vending and affixing machines. Some coils, including most U.S. coils, have a straight edge on two parallel sides and perforations on the remaining two parallel sides. Some coils are backprinted with sequence or counting numbers.
Collateral material: Any supportive or explanatory material relating to a given stamp or philatelic topic. The material may be either directly postal in nature (post office news releases, rate schedules, souvenir cards, promotional items) or nonpostal (maps, photos of scenes appearing on stamps).
Combination cover: Cover bearing the stamps of more than one country when separate postal charges are paid for the transport of a cover by each country. Also stamps of the same country canceled at two different times on the same cover as a souvenir.
Commatology: Specialized collecting of postmarks. This term was invented before World War II to describe postmark collecting. It is rarely used. Usually, collectors refer to postmark collecting or marcophily.
Commemorative: A stamp printed in a limited quantity and available for purchase for a limited time. The design may note an anniversary associated with an individual, an historic event, or a national landmark. See also Definitive.
Compound perforations: Different gauge perforations on different sides of a single stamp. The sides with the different gauge measurements are usually perpendicular.
Condition: The overall appearance and soundness of a stamp or cover. Positive condition factors include fresh full color, full original gum on unused stamps, and so on. Damage such as creases, tears, thinned paper, short perforation teeth, toning and so on negatively affect condition.
Controlled mail: A system in which the mailer selects philatelically desirable issues for outgoing mail, arranges for a specific manner of cancellation and secures the stamps' return by the addressee. In some cases such controlled mail operations may provide rare examples of specific rate fulfillment, or other similar postal use.
Copyright block: Block of four or more United States stamps with the copyright notice marginal marking of the United States Postal Service. The copyright marking was introduced in 1978 and replaced the Mail Early marking.
Corner card: An imprinted return address, generally in the upper-left corner of an envelope, from a commercial, institutional or private source, similar to business card or letterhead imprints.
Counterfeit: Any stamp, cancellation or cover created for deception or imitation, intended to be accepted by others as genuine. A counterfeit stamp is designed to deceive postal authorities.
Cover: An envelope or piece of postal stationery, usually one that has been mailed. Folded letters that were addressed and mailed without an envelope and the wrappers from mailed parcels are also covers.
Crash cover: A cover that has been salvaged from the crash of an airplane, train, ship or other vehicle. Such covers often carry a postal marking explaining damage or delay in delivery.
Crease: A noticeable weakening of the paper of a stamp or cover, caused by its being folded or bent at some point. Creases substantially lower a stamp's value. Creases particularly affect cover values when they extend through the attached stamp or a postal marking. Stamp creases are visible in watermark fluid.
Cut cancellation: A cancellation that intentionally slices into the stamp paper. Often a wedge-shaped section is cut away. On many issues, such cancellations indicate use of postage stamps as fiscals (revenues) or telegraph stamps rather than as postage. Cut cancellations were used experimentally on early United States postage stamps to prevent reuse.
Cut square: A neatly trimmed rectangular or square section from a stamped envelope that includes the imprinted postage stamp with ample margin. Collectors generally prefer to collect stationery as entire pieces rather than as cut squares. Some older stationery is available only in cut squares.
Cut-to-shape: "A nonrectangular stamp or postal stationery imprint cut to the shape of the design, rather than cut square. Cut-to-shape stamps and stationery generally have lower value than those cut square. One of the world's most valuable stamps, the unique 1856 British Guiana ""Penny Magenta"" (Scott 13), is a cut-to-shape stamp."
Cylinder: A curved printing plate used on a modern rotary press. The plate has no seams. For United States stamps, cylinders are used to print gravure stamps. See also Sleeve.
Cancellation: A marking intended to show a stamp has been used and is no longer valid as postage. Modern cancels usually include the name of the original mailing location or a nearby sorting facility and the date of mailing. Most cancellations also include a section of lines, bars, text or a design that prints upon the postage stamp to invalidate it. This part of a cancel is called the killer.
CTO: "Canceled-to-order. Stamps are ""canceled to order,'' usually in full sheets, by many governments. The cancels may be printed on the stamps at the same time that the stamp design is printed. A stamp with a cancel and with full gum is likely a CTO stamp, as CTOs do not see actual postal use. CTO stamps are sold to stamp dealers at large discounts from face value. Most catalogs say whether they price CTO stamps or genuinely used stamps."
Charity stamp: "A stamp sold at a price greater than postal value, with the additional charge dedicated for a special purpose. Usually recognized by the presence of two (often different) values, separated by a ""+'' sign, on a single stamp."