noun: A shortened form of a word or phrase used chiefly in writing to represent the complete form, such as Mass. for Massachusetts or USMC for United States Marine Corps.
Angliško žodžio naudojimo pavyzdys:
Fiat and Alfa separately designed two analogous models, named in military terms AR 51 (the abbreviation is short for 'Autoveicoli da Ricognizione' and the number a reference to its year of introduction of 1951) both with 1900 cm3 engines.
In case you didn't know, that abbreviation is for 'Release Candidate'.
So it goes with abbreviations; if you want to be literal, an abbreviation is an abbreviated form of something.
In the New York Times, the preferred abbreviation is number-apostrophe-s (e.g., 90's), while in many other publications the preferred abbrevation is apostrophe-number-s (e.g., '90s).
An abbreviation is something like ‘etc.’, which is marked, if at all, with a full stop.