Pack and Send : A pilot retail service offered at selected post offices that allow customers to bring in any mailable item to have it securely packaged and, if they wish, mailed.

Packet : A presorted unit of all different stamps. This is one of the most common and economical ways to begin a collection.

Pair : Two stamps that are joined in the original state of issue. e.g. Vertical pair, Horizontal pair, Coil pair.

Pane : A full "sheet" of stamps as sold by a Post Office or Part of a sheet of stamps divided by a margin from the remainder of the sheet. Also, Booklet pane.

Par Avion : French for mail transported "by air."

Peel and Stick : Australian terminology for Self Adhesive.

Perforations : Lines of small holes or cuts between rows of stamps that make them easy to separate.

Perfin : Normal stamps which have initials formed in the stamp by perforations. Often used by commercial organizations as a security measure.

Philately : The collection and study of postage stamps and other postal materials.

Phosphor Stamps : Stamps which have been coated with a 'fluorescent' substance for detection in the mail sorting system.

Phosphor bands : A narrow line of 'fluorescent' substance across the face of a stamp. Stamps can have one or two bands and the position may vary.

Photogravure : Printing using the recess process.

Pictorials : Stamps with a picture of some sort, other than portraits or static designs such as coats of arms.

Pigeon Post : As it sounds. Used as long ago as the 1870 - 1872 Franco-Prussian war during the siege of Paris and also in Australia by the Great Barrier Pigeongram Service.

Plate Block (PB) (or Plate Number Block) : A block of stamps with the margin attached that bears the plate number used in printing that sheet.

Plate number : The number of the printing plate which was used to print the sheet of stamps and marked in the sheet margin.

Postage due : A stamp which is used by the postal authorities to indicate that the correct postal fee has not been paid and the sum due for the delivery of the item. Same as 'To Pay' labels.

Postal Cards : See "stamped postal cards."

Postal Inspection Service : The investigative arm of the Postal Service responsible for internal audits and investigating criminal acts involving the mails and misuse of the postal system.

Postal Stationery : Envelopes, aerogramme, stamped postal cards, and letter sheets with printed or embossed stamp designs.

Postcards : Commercially-produced mailable cards without imprinted postage.

Postmark : The postal service's official mark on the letter, envelope, letter sheet or postcard to show the time, date and place of posting, and to cancel the stamp.

Postmaster General (PMG) : The chief executive officer of the Postal Service

Precancels : Stamps cancelled by a proper authority prior to their use on mail.

Prestige booklet : A booklet of stamps issued by the postal authorities commemorating some event or particular subject or special topic.

Priority Mail : Priority Mail provides two to three day delivery service.

Processing and Distribution Center (P&DC) : A large mail sorting and dispatching plant that serves as a hub for mail originating from post offices, collection boxes and customer mailboxes, and large-volume mailers in a designated service area.

Proof : A trial impression taken from an original die or printing plate.

Provisional : A stamp, usually overprinted or surcharged, issued for temporary use.

P.T.S.A. : Priced to Sell At. A term used in auctions where stamps in a lot have been previously priced for retail or approval purposes.