Unhinged : A stamp without hinge marks, but not necessarily with original gum.

Universal service : The Postal Service's mandate and commitment to the nation to provide mail delivery service at uniform and reasonable rates to everyone, everywhere, six days a week.

Unused : An uncancelled stamp, not necessarily 'mint'.

Used : A stamp which has been postally used and appropriately postmarked.

Used abroad : Where stamps from one country are used and cancelled in another. This is quite common in cases such as British Colonies or Possessions. Spain and France also were countries that issued stamps that were used in other areas of the world over which they had influence. These stamps can only be distinguished by the postmark applied.