Let me begin by asking a question: how do we define the term, “the Japanese language”? Odds are that those both unfamiliar and fairly familiar with Japan alike will answer at once, “the language that is spoken by people in Japan.” And of course, they would be quite right, up to a point.
Pressed for a similar definition of the English language, the answer would require more thought, since English is patently not just the language spoken in England by the English but, like French and Spanish, is spoken in a variety of local forms throughout a great number of countries of the world, legacies of former empires and the commercial and cultural webs spun between countries around the world. Arabic, too, is the official language of over twenty countries and Chinese in one form or another is spoken widely throughout East and South East Asia and in the countries of the Chinese diaspora.
In the case of Japanese, while geography likewise plays a part in definition, the geography is limited to that of the Japanese archipelago. Japan once had an empire too, and Japanese was spoken in its colonies, as we shall see, and to some extent remains so: in the former colony of Taiwan, for example, elderly people who were children during the days of the Japanese empire were brought up to speak Japanese as their first language and speak it still. Yet for most people the definition given above is the first which springs to mind.