  in philately, the term cover pertains to the outside of an envelope or package with an address, typically with postage stamps that have been cancelled and is a term generally used among stamp and postal history collectors. the term does not include the contents of the letter or package, although they may add interest to the item if still present. cover collecting plays an important role in postal history as many covers bear stamps, postmarks and other markings along with names and addresses all of which help to place a cover at a given time and place in history.postal history society == history ==  the term originates from the practice of covering a letter by folding a separate sheet about it to physically protect it and prevent infringement of confidentiality. in the first half of the 19th century it became the fashion to cut the cover into a diamond or lozenge shape. this was the precursor of the version of the envelope known today. its convenience and popularity led to the lozenge design being adopted for the special pre-paid postage envelopes and covers issued in 1840 after postal reforms were introduced by rowland hill and others. ==categories== there are several different basic categories for covers. names for cover types is also terminology usually used by collectors of stamps and postal history. there exist a wide variety of covers that can fit into several basic categories. the categories begin with the most common types of collectible covers, such as first day covers or first flight covers. sometimes there will be an area of overlap in the subject of categories. for example there are first day covers that were also sent with mail aboard airplanes on first flight mail runs. event covers can also include, first flights, or other types of covers. a military cover sent to a head of state can also be referred to as a historic cover.{{cite web |url=http://www.linns.com/howto/refresher/covers_20070716/refreshercourse.aspx |author=david dobson, author of 'scottish emigration to c
Envelopes Philatelic_terminology