Short set

An incomplete set of stamps, usually lacking either the high value or one or more key values.

Sheet

A complete unit of stamps as printed. Stamps are usually printed in large sheets and are separated into two or more panes before shipment to post offices.

Shade

The minor variation commonly found in any basic color. Shades may be accorded catalog status when they are very distinctive.

Se-tenant

French for “”joined together.” Two or more unseparated stamps of different designs, colors, denominations or types.

Set

Stamps sharing common design elements, often issued at one time and usually collected as a group.

Service inscribed

A stamp with wording as part of the initial printed design that identifies the mail-handling service for which the stamp is intended, such as “”Presorted First-Class.”" See also Precancel.

Series

A group of stamps with a similar design or theme, issued over a period of time. A series may be planned or may evolve.

Semipostal

A stamp sold at a price greater than postal value, with the additional charge dedicated for a special purpose. Usually recognized by the presence of two (often different) values, separated by a “”+” sign, on a single stamp.

Selvage

The marginal paper on a sheet or pane of stamps. Selvage may be unprinted or may contain printer’s markings or other information.

Self-adhesive

Stamp gum that adheres to envelope paper by the application of pressure alone. Most self-adhesive stamps are sold on a coated paper release liner. See also Liner, Linerless, Water-activated.