I am often asked why English is such a difficult language to learn, for non-native speakers. In fact, how hard it is to learn depends on what your native language is; and this follows as languages are more (or less) closely related to one another; if your mother tongue is more similar, in terms of sounds, vocabulary and grammatical patterns to another--for instance you're a speaker of Dutch or German--then English will be easier to learn. But if you speak a language that comes from a more distantly related tongue--say Japanese--then English is more likely to prove a tougher nut to crack.
There are over 6,000 languages spoken in the world today, but some 2,000 of them count fewer than 1,000 speakers. Moreover, just 15 accounts for half of the languages spoken in the world.