Cachet : A design on an envelope describing an event. Cachets appear on first day of issue, first flight and stamp exhibition covers, etc.

Cancellation : A mark placed on a stamp by a postal authority to show that it has been used.

C.D.S. : A circular date stamp used for cancelling the stamp by the postal authorities.

Centering/Centered : The position of the design on a postage stamp. On perfectly centered stamps the design is exactly in the middle. e.g. Well Centered - an equal margin between the edges of the stamp and the design.

Changling : A stamp whose original color has changed.

Charity Stamp : A stamp that has an additional charge for charity.

Cinderella : Any stamp-like label without an official postal value.

Classic : An early stamp issue which is rare and of high quality. However it is not always true. They aren't necessarily rare.

Coils : Stamps issued in rolls (one stamp wide) for use in dispensers or vending machines.

Color Shift : Where the design of the stamp has more than one color and these are applied at different times in the process of printing and the positioning of the colors is incorrect in relation to the intended design.

Comb Perforation : The perforations of a stamp formed by the pins of the perforating machine which are arranged like a comb.

Commemoratives : Stamps issued to commemorate anniversaries, important people, special events, or aspects of national culture.

Compound Perforations : Different gauge perforations on different (normally adjacent) sides of a single stamp.

Condition : Condition is the most important characteristic in determining the value of a stamp. It refers to the state of a stamp regarding such details as centering, color, and gum.

Condominium : A Territory over which there is joint rule by two Powers. An example of this is the Anglo - French New Hebrides Condominium whose stamps are inscribed in English and French.

Control Marks : The numbers or letters in the margins of a sheet of stamps, normally for the benefit of the Post Office in stock control and accounting.

Cover : An envelope that has been used in the postal system and sent through the mail.

Cracked Plate : A term used to describe stamps which show evidence that the plate from which they were printed was cracked.

Customer Perfect! : A quality process management system that builds customer satisfaction and excellence into every process and procedure of the Postal Service.

Cylinder Number : The number in the margins of a sheet of stamps which identifies the cylinder which has been used in the production process.