Abbreviations/Initialisms, Contractions, Acronyms
The New Paper writer SM Ong complains that ‘[PMET is not] even a word, but an unpronounceable acronym’ (New Paper on Sunday, 1 March 2009).
Of course it’s unpronounceable — it’s not even an acronym!
‘Abbreviation’ is the general term for any shortened word. It comprises contractions, abbreviations/initialisms, and acronyms.
Contractions are words that have been shrunk in the middle, e.g. Prof, Mr, Adm. (American usage has a full stop at the end of all of these, whereas conservative British usage uses a full stop only if the full form of the word ends in a different letter: hence Prof. for professor and Adm. for admiral, but Mr for mister. Current British usage, however, has largely dispensed with full stops.)
Abbreviations formed from initials and which are not pronounced as words are known simply as abbreviations or initialisms. In Singapore, common abbreviations/initialisms include ERP, MRT, PAP, CPF and COE.
Acronyms, on the other hand, are abbreviations/initialisms which are pronounced as words, e.g. NATO (North Atlantic Treaty Organization) and ASEAN (Association of South East Asian Nations).
Some abbreviations in Singapore are initialisms for some speakers and acronyms for others. For instance, some people say ‘mert’ for MRT (apparently in jest) and ‘nell’ for NEL — for them, these would be acronyms rather than initialisms.