English has the largest vocabulary on earth with tens of thousands of “borrowed” words. There are 171,474 words currently in use in English. There are over 47,000 obsolete English words.
English has more words than any other language (there are some languages, such as Finnish, where sentences can be effectively compressed into one new word, making the number of words nearly infinite). But English has the most words that are singly defined in dictionaries.
That makes it very difficult to learn.
“Business” English is a subset of English (under 5,000 words) that is widely used internationally. I have read that people meeting internationally in groups will use “Business” English as a common language, with the native English speaker being at a disadvantage because he will naturally use a wider vocabulary the non-native speakers cannot understand.