abbreviation [abbreviations](shortened or contracted form of a word or phrase) noun [UK: ə.ˌbriː.vi.ˈeɪʃ.n̩] [US: ə.ˌbri.vi.ˈeɪʃ.n̩]
acronym [acronyms](word formed by initial letters) noun [UK: ˈæ.krə.nɪm] [US: ˈæ.krə.nəm]Do you know where the acronym PDF comes from? = Sa da dove viene l'acronimo PDF?
initialism [initialisms](term pronounced letter by letter) noun