We usually write abbreviations without full stops in British English.
Mr (NOT -Mfr) = Mister Ltd = Limited (company) kg = kilogram the BBC = the British Broadcasting Corporation the USA = the United States of America NATO = the North Atlantic Treaty Organization OPEC = the Organization of Petroleum Exporting Countries
Some abbreviations are made from the first letters of several words. We usually pronounce these with the stress on the last letter. the BBC Iba bi:bi:'si:/ the USA Iba ju'.es'ei/
Some of these abbreviations are pronounced like one word. We do not usually use articles with these. NATO /'neitau/ (NOT ihe NATO) OPEC I'aupek/ (NOT -the OPEC)