Terms

Denominational Stamp - A stamp that is for a specific dollar value, opposes to a specific usage.

Non-Denominated Stamp - A stamp with a usage value, that is good for a specific use. The purpose of these stamps was to avoid having to buy additional stamps when price increase. 

• In the USA, this is referred to as a "Forever Stamp."

Semipostal Stamp: Semipostal is a type of stamp that raises money for a particular case, often a charity. The stamp is sold at a higher rate than normal stamps of that class. The surcharge is then donated to that cause.