Think of everything that gets called English, then keep only the part that travels. Words like water, computer and airport work in Taipei, Lagos, Sydney and Chicago alike. Words that belong to one place, such as lorry or freeway, sit outside that shared core. Writers aim at this core when their readers come from many countries, which is why manuals and airport signs sound the way they do. It is singular and uncountable, so you say World English is..., not a World English. Another common name for the same idea is international English.

English travelled, settled in many places, and in each place it grew its own shape. The words change, the sounds change, and so do the everyday turns of phrase. These are systems in their own right, not broken versions of anything. When people talk about several of them at once they usually write the plural, World Englishes, and that plural is standard in language study. Note a small difference: this use is uncountable in one reading, countable in another, and that countable reading excludes British and American English from the group. The wider reading is kept here.