Definitive stamps are sometimes called the “workhorse” of the postal system. They’re also known as regular-issue stamps. They pay postage on everyday mail and are issued in lots of denominations. Often a particular definitive stamp design is used for long periods of time, and sometimes reprinted to replenish supplies.
Definitives are fun to collect. There may be small difference among stamps, which at first glance appear the same. Characteristics to look for include small changes due to variations in printing plates or printing methods; a different shade or color; margin dates, watermarks (on older U.S. stamps), perforations, microprinting, and type of gum (self-adhesive or water-activated).
A Commemorative is a stamp issued to honor an important person, event, or anniversary. It’s printed in smaller quantities than definitives, and is sold for a limited time, usually a few months. Unsold stamps are generally destroyed.
The first U.S. commemorative stamps were issued in honor of the 1893 World’s Columbian Exposition. The 16-stamp series depicted the various stages of Columbus’ voyages to the New World. Today these stamps are highly valued by collectors. As you can see, commemoratives make America’s history come alive.