* Definitive stamps are found on most mail. They feature former presidents, statesmen, prominent persons and national shrines. Their denominations range from 1 cent to 14 dollars. Definitives are placed on sale for an unlimited period, since they're printed in large quantities for specific postal rates. New definitives are issued when the postage rates change or a new series is introduced.
* Commemorative stamps are issued in observance of historical events in honor of noted Americans and on topics of national importance. Each commemorative issue is printed in limited quantities to be sold for a limited period of time (usually 60 days). Comemmoratives are usually larger and more colorful than definitives. Only a limited number of each commemorative is printed, and most post offices only have them for a few months. The U.S. Postal Service's Philatelic Fulfillment Service Center also offers commemorative stamps by mail order for about one year after they are issued.
* Special stamps supplement each year's regular stamp issues. They include the Christmas and Love stamps.
* Airmail stamps are mainly used for sending mail overseas.
* Booklet stamps come in small folders that contain panes of 3 to 20 stamps each. Gummed booklet stamps have at least one straight edge.
* Convertible Booklets are self-adhesive panes with a thin horizontal paper strip at the center or near the bottom that can be removed so that the pane can be folded twice, making it easy to carry in a pocket or purse.
* Coil stamps are issued in rolls for use in dispensers, as well as affixing and vending machines. Each coil stamp has two straight edges and two edges with either slitlike cuts or little holes, called perforations.
* Special Purpose Stamps are issued for a specific purpose such as Express Mail and International airmail. These stamps are printed for indefinite periods and are seldom revised except for a rate change. While these stamps are intended for a specific service, they are valid for all postage purposes