WWII is the short written form of World War II — the war of 1939 to 1945, fought across Europe, Asia, Africa and the Pacific. The 'II' is the Roman number two, so you say the whole thing aloud as 'World War Two'. Like WWI, this abbreviation lives on the page, not in the mouth: you will see it in timelines, captions, notes, headlines and search terms, but a person speaking simply says 'World War Two'. In careful full-sentence writing, most writers spell it out as World War II or, especially in Britain, the Second World War. It is worth knowing that different countries start counting from different dates and give the war different names — in Chinese-speaking places the fighting in Asia is often dated from 1937 and remembered under its own name, so a Taiwanese student and a British student may be picturing rather different lengths of time when they use the same three letters.