Countries and regions have two letter abbreviations (ISO 3166-1) as do languages (ISO 639-1). So do chemical elements, US states, and books filed using the Library of Congress system.
I was curious how many of the 676 possible two-letter combinations are used by the abbreviation systems above. About two thirds, not as many as I expected.
There are 798 abbreviations in the lists mentioned, but a lot of overlap. For example, FR represents the country France, the language French, and the chemical element Francium.
There are five abbreviations that are part of all five lists: GA, LA, MT, NE, and PA.
- GA (Gabon, Irish, gallium, Georgia, cartography)
- LA (Lao People’s Democratic Republic, Latin, lanthanum, Louisiana, history of education)
- MT (Malta, Maltese, meitnerium, Montana, music instruction)
- NE (Niger, Nepali, neon, Nebraska, print media)
- PA (Panama, Punjabi, protactinium, Pennsylvania, Greek and Latin language and literature)