There are so many words in the English language that either imply or blatantly mean one. In must case the word unit means one. Solo is another one, but that means by yourself too. You could be a Cyclops and have complete tunnel vision for one definition. We like the word this way, lots of diversity. It makes life fun otherwise there would be no surprises in life.
It now time to fly off (or roll off) on our unicycle...