Block	Two or more stamps affixed together.
Booklet	Stamps that are enclosed in the original retail container.
Cachet	(pronounce ‘ka-shay') - A design printed or stamped on an envelope describing or commemorating an event. Cachets can be for any event e.g. on first day of issue, first flight and stamp exhibition covers, etc.
Cancel	A marking that shows a stamp has been used. Modern cancels usually include the location of the post office from which the item is mailed and the date of mailing. Some also include a section of lines, bars, text or a design that "kills" the value of the stamp. This part of a cancel is called the killer.
Cliche	(pronounce clich'e \Cli`ch['e]), n. [F. clich['e]), from clicher to stereotype.] A stereotype plate or any similar reproduction of ornament, or lettering, in relief.
Cover	Typically with semi official stamps, there is a Canada Postage stamp on the front and the Semi Official stamp on the back of the envelope.
Essay	Presentation of a stamp before it is selected for a stamp issue.  Some essays are not official and are designated accordingly.
Frank	An indication on a cover that postage is prepaid, partially prepaid or that the letter is to be carried free of postage. Franks may be written, hand stamped, imprinted or affixed. Free franking is usually limited to government correspondence or soldiers' mail. Stamps are the modern method of franking a letter.
Gutter	The selvage, either unprinted or with plate numbers, advertising or accounting or control numbers, between the panes of a sheet of stamps.
Imperf.	(short for Imperforate), Stamps printed in sheets without perforation or other means of separation.
Proof	Presentation of a stamp before it goes into production.
Pane	Stamps are generally printed in sheets then cut into more functional panes.
Sheets	Stamps as they were printed.  Not all semi official stamps were printed in sheets but all were printed in panes.
Selvage	The unprinted marginal paper on a sheet or pane of stamps.
Tęte-bęche	(pronounce 'tet besh'), adj. Of, relating to, or being a pair of postage stamps printed with one upside-down in relation to the other, either deliberately or accidentally.  [French : tęte, head (from Old French teste, from Late Latin testa, skull. See tester1) + bęche(short for obsolete béchevet, double head of a bed, from Old French : bes-, twice from Latin bis; see bis + chevet from Late Latin capitium, opening for the head in a tunic, from Latin, head covering, from caput, capit-, head.]  Stamps become "tęte-bęche" when their plates are printed by the "work and turn" process.]