a small sheet of one or more stamps, valid for postage, usually issued in conjunction with a philatelic exposition.
A small sheet of stamps, including one value or a set of stamps. A souvenir sheet usually has a wide margin and an inscription describing an event being commemorated. Stamps on a souvenir sheet may be perforated or imperforate.
A small sheet containing one of each stamp in a given issue sold alongside the set of individual stamps. They are also available in FDC and in Presentation Packs.