Acronyms formed from a string of initials and usually pronounced as individual letters (as in "FBI" from "Federal Bureau of Investigation", and "e.g." from Latin ) are sometimes more specifically called or . Occasionally, some letter other than the first is chosen, most often when the pronunciation of the name of the letter coincides with the pronunciation of the beginning of the word (example: "BX" from "base exchange"). Acronyms that are usually pronounced as words, such as "AIDS" and "scuba", are sometimes called word acronyms, to disambiguate them more clearly from initialisms, especially since some users of the term "initialism" use "acronym" in a narrow sense meaning only the type sounded out as letters. Another sub-type of acronym (or a related form, depending upon one's definitions) is the syllabic abbreviation, which is composed specifically of multi-letter syllabic (even multi-syllabic) fragments of the abbreviated words; some examples are "FOREX" from "foreign exchange", and "Interpol" from "international" + "police", though its full proper name in English is International Criminal Police Organization). Usually the first syllable (or two) is used from each major component word, but there are exceptions, such as the US Navy term "DESRON" or "DesRon" from "destroyer squadron".