I rather say "international" language. It doesn't matter how many people speak it.
What matter is that you can't learn all languages in the word. When you need to speak to a stranger, let's say a german trying to speak a chinese, you have to speak a third language that both can understand. Hence the one international language that all should use when they want to speak to someone stranger, unless they know the specific local langage of that guy. No matter how many chinese or russians there is around, i won't gonna learn ten language when the english is enough to speak both to the chinese and the russian, or even the brazilian, vietnamese, koreans etc...