Face Value : The monetary value of a stamp as printed on the stamp in the relative currency of the country of issue.

Fake : A genuine stamp that has been altered in some way to make it more attractive to collectors. It may be repaired, reperforated, or regummed to resemble a more valuable variety.

First Day Cover (FDC) : An envelope with a new stamp and cancellation showing the date the stamp was issued.

First Day Ceremony Program : A program given to those who attend first day of issue stamp ceremonies. It contains the actual stamp affixed and postmarked, a list of participants, and information on the stamp subject.

First-Class Mail : A class of mail including letters, postcards and postal cards, all matter wholly or partially in writing or typewriting, and all matter sealed or otherwise closed against inspection.

Fiscal : A stamp issued for revenue or tax purposes and not as a postage stamp.

Flaw : A fortuitous blemish on a stamp, a printing fault.

Forgery : A fraudulent copy of a genuine postage stamp, overprint or postmark.

Franks : Written, hand-stamped, or imprinted markings on the face of the cover indicating that it is carried free of postage. Franking is usually limited to official government correspondence.

Freak : An abnormal variety of stamps occurring because of paper fold, over-inking, perforation shift, etc., as opposed to a continually appearing variety or a major error.

Fugitive Colors : These are inks which are specially produced in order that they will change or wash out if there is an attempt to tamper with the stamp such as, removing the postmark. This is meant to deter the reuse of stamp already passed through the Postal System.