We have all heard the words astronaut and cosmonaut and know their meaning. But what is a taikonaut? In fact, the three words are synonyms: an individual who is trained to travel in spacecraft or has flown in outer space. So, why do we need three words if they have exactly the same meaning? Well, the truth is that on an etymological level they aren't exactly the same. Let's see what are the similarities and differences between the three terms.