0 (number)

0 (zero) is a real number and is the integer between 1 and -1. It is also the numerical digit which represents itself. As a number, it is used to signify a value of nothing, and as a digit, it is a placeholder for place value systems.

History

The number zero was invented twice - once in India and once in Mesoamerica. This invention is considered especially significant because it required a considerable cognitive leap to achieve and because it opened the door to a host of new applications for numbers.