Schiffspost - (German) Ship post.
Seal - A device for making an impression in wax, clay, paper, or some other medium, including an embossment on paper, and also the impression thus made. The original purpose was to authenticate a document, a wrapper for one such as a modern envelope, or the cover of a container or package holding valuables or other objects. The sealing process is essentially that of a mold, with the final image represented on the device for making the impression by a mirror-image design, incised in sunken- (or counter-) relief or intaglio.
Se-tenant - French term meaning "Joined together", used to describe stamps or labels printed from the same plate that adjoin one another but have different designs, value or some other aspect.
Setting - The exact geometrical arrangement of the type used for an overprint.
Sea Post Service - Bona fide post offices that operated on ships traveling regular routes.
Separation - A general term applied to any means provided for separating stamps. The earliest stamps, and some more recent issues, had no provision for this. Such stamps are usually called 'imperforate'. Many methods have been developed for removing individual stamps from sheets. These processes are termed 'perforating' and 'rouletting'.
Sheet number - Colored numbers printed consecutively on sheets of stamps which identify individual sheets as well the number of sheets printed.
Single circle postmark - A circular date handstamp contained within a single circle.
Skeleton - A date handstamp made up of loose type.
Slogan - A postmark containing a message or announcement.
Soldi - Lombardy-Venetia currency, under Austrian rule equal to the Austrian Kreuzer (1/60 of Gulden). As from 1863, stamps of Lombardy-Venetia were used in the Austrian Post Offices in the Ottoman Empire, but after the loss of Lombardy-Venetia in 1867, Austria had to issue special stamps; they were identical in appearance to Austrian stamps of the period, but denominated in soldi and florins. In 1886 this was changed to Para and Piaster to match Turkish currency, first by surcharging the existing stamps of the offices, then regular Austrian stamps.
Soldier's Letter - The term applied to a letter posted by a serving soldier. Carried at a reduced "privilege" rate, or free of charge.
Souvenir sheet - A particular postal issue typically used to commemorate special events, incorporating one or more stamps. It is produced on small format paper with wide margins, often printed with a unifying background and/or title. The stamps may or may not be perforated, and usually differ in design and possibly denomination from each other.
Special Delivery Service - A service which provided prompt delivery of all letters franked accordingly.
Specimen - (i) A single copy of a postage stamp or other philatelic item. (ii) More properly, a postage stamp overprinted 'specimen' and issued by the postal authority as an example of a new issue.
Surcharge - An overprint on the face of a stamp which changes, adds to, or confirms its face value.
Scott - Scott catalogue of United States Stamps - Scott Publication Co.
Steichele - "Handbook of Holy Land Philately - The Foreign Post Offices in Palestine 1840-1918" - Anton Steichele Volume I & II - Published 1991 by World Philatelic Congress of Holyland & Judaica Societies (W.P.C.)
SG - Stanley Gibbons stamp catalogue.
Suleymaniye - Revenue Stamps of Ottoman Empire & early period of Turkish Republic, Emir Eray Suleymaniye - Ankara 2010