English is dominant, not because the number of speakers, but because they are so widespread. Mandarin has more, but they area almost all in China, whereas ther

English is dominant, not because the number of speakers, but because they are so widespread. Mandarin has more, but they area almost all in China, whereas there is hardly a corner of the earth where you can't find an English speaker. So if you plan to travel to a lot of places, the most efficient language to learn is English. Between any two non-neighboring countries, the language with the highest number of mutual speakers is almost certainly English. I don't think any other language in history has had this level of network effect.