Zero means nothing. When you add zero to the number one, you get the number one. If your mother says your new boyfriend is a zero, she thinks he's got nothing going for him.
You might know zero as 0, zilch, zip, nothing, or nada. While it is a number of no value, without it we wouldn't be able to count beyond 9. The temperature at which water freezes is zero degrees Celsius. And if you got a zero on a test, it means that you answered every single question wrong.