Existence of multi in US English Yes, the prefix multi is valid in American English, and usually used unhyphenated You can see dozens of examples on Wiktionary or Merriam-Webster If your grammar and spelling checker fails to accept it, it should be overridden manually
Is there a word for a person who is able to focus on multiple tasks at . . . 2 Multi-tasker is probably the most widely recognized English phrase for this Someone able to do remarkable feats of intellect or creativity, like Leonardo writing and drawing at the same time, is often called a prodigy That doesn't necessarily imply doing multiple things at once, but it's the sort of thing that a prodigy might be able to do