Term applied specifically to certain stamps produced by De La Rue for Great Britain, 1862-80, from plates which were not subsequently put into normal production. De La Rue submitted to the Board of Inland Revenue the first six sheets of stamps produced from each plate. These stamps were imperforate but gummed and watermarked. The Board retained one sheet as the Imprimatur and the other five sheets were either destroyed or perforated and put into circulation. Normally these five sheets would be the same as all others produced from the same plate, but sometimes plates were modified or scrapped, or a change was made in the colour used for the normal printing. The resultant stamps from the five sheets were therefore classified as Abnormals. Only 12 types of Abnormal have so far been recorded, although there are a further nine plates which were registered but from which no stamps are known to exist.

Various products and tools commonly used by the stamp collector, including hinges, mounts, stamp tongs, perforation gauges, stock books and magnifiers. Stamp albums, catalogs and philatelic literature can also be regarded as accessories.

1) The gum on the back of a stamp or label. Some stamps have been issued with no adhesive. Stamp adhesive may be water-activated or pressure-sensitive (self-adhesive). 
2) A word generally referring to a stamp that may be affixed to an article to prepay postal fees, in contrast to a design printed directly on an article, as with postal stationery. An adhesive can also refer to a registration label or other label added to a cover.