As the world has become closely connected, we need a “world common language”, with which we can communicate with each other and share our thoughts, ideas, and feelings.
Some say that English must be the one because it is now widely used all over the world. I don't think so.
English is certainly the most popular language in the world. According to a research, about 1.75 billion people, 25% of the world total population of 7 billion, are now using English as an international communication tool for businesses, researches, and so on.
But you must know that, among that 1.75 billion, English native speakers is only 0.39 billion, 22% of the total number. The remaining 78% are non-native English speakers. They are Europeans, South Americans, Arabs, Africans, and Asians (including us). The language they use is not "native English", but "International English".
International English is similar to native English because it is a child of native English, just as native English is a child of ancient German language. But, as children are not the same as their parents, International English is not the same as native English.
The two languages are very different in many ways. The grammar of International English is much simpler than that of native English, and easy to learn for everyone in the world. Some grammatical mistakes can be accepted as long as they don’t cause serious troubles in communication. Any difficult vocabulary and complex expressions are avoided in International English. Any pronunciation can be accepted in International English as long as it is understandable. To summarize, International English is much simpler and more flexible than native English.
As International English is a world common language for everyone in the world, even English native speakers have to learn it. A study shows that American English is very difficult to understand for most of the people in the world. And, surprisingly enough, the study also shows that Japanese English is very easy to understand for all the people in the world. Japanese English is an excellent International communication tool!