There are subtle differences between those. A global language I think is the best way to describe English, in the sense that many people from many countries speak English. A universal language would be something that any one person in the world could understand, regardless of which language they speak. Things like body language and math would fall into that category. A world language seems vague to me. I think of "a world language" as any language spoken in the world. English, Spanish, Dutch, Korean. Doesn't seem very descriptive.