Let's get complicated, (But for fun
Here is a list of acronyms and terms across Philately
Take from it, what you will, Philately can be as broad as you wish,
or as specialised as you want to make it.
"Have fun" (Arthur Mongan)
All excerpts from "Askphil"
AFDCS: American First Day Cover Society.
Alternate cancel: any First Day cancellation from the official First Day city, other than the official First Day USPS
1: a rubber stamp or printed impression on an envelope which describes the event for which the envelope was mailed; cachets are used for first days of issue, first flights, naval events, stamp exhibitions, etc.
2: rubber stamp or seal, not postal.
3: small marks made by dealers, experts on backs of stamps as marks of authenticity or identification.
4: can be privately applied or officially applied by a post office; also known as "Signum."
Cancel, Official: official USPS postmark at First Day of Issue site.
any item, besides a cover, postcard or envelope, that has been cancelled on the First Day and doesn't fit any of
the regular collecting categories
F D C: see First Day Cover. F D I: see First Day of Issue.
First day: the day on which a stamp is first officially sold by the Post Office.
First day ceremony program: special items created for distribution to guests at first-day ceremonies
First day cover: a newly issued stamp affixed to an envelope and postmarked on the first day of sale at a city designated by the Postal Service.
First Day Objects (FDO): various non-philatelic objects to which a stamp and first day cancel was applied.
First day of issue (FDOI): the day on which a stamp is initially placed on sale by postal authorities.
First day of issue office: a post office authorized to sell a new postage item on the first day of sale.
First day of rate: postmark denoting the first day of usage of a new postal rate.
New issue poster: Post Office Department poster, started in 1959, where collector affixed new issue stamps to the poster and had them canceled on first day of issue.
Paraphilatelic: post office announcements of a new stamp, first day of issue ceremony programs, souvenir pages, etc.
Philadelpia: misspelling of Philadelphia on cancellation of first day cover for "Honoring the Teachers of America" issue, July 1, 1957.
Philography: term for autographed first day covers.