Zero

Leonardo Bonacci (c. 1170 to c. 1250) also known as Fibonacci (or Filius--son of--Bonacci), was an Italian medieval mathematician. First, he introduced Arabic (originally Indian) numerals to the West. Second, he described the "Fibonacci number sequence," a beautiful and naturally-occurring spiral progression found in shells and flowers, even galaxies, and reproduced by artists from ancient Greek to post-modern as an ideal of proportion, the Golden Mean.

In 1202, Fibonacci published Liber Abaci (Book of Calculation), the first section of which introduces the Hindu–Arabic numeral system that he had encountered in the North African city, Bejaia. He tells us that the numerals 1, 2, 3, 4, 5, 6, 7, 8, and 9 come to us by way of India. The sign 0, he says, which "the Arabs call zephyr," صِفْر ‎(ṣifr, “nothing, cipher”), was originally śūnya in Sanskrit: शून्य.

Disclaimer: the first time I learned about the Fibonacci sequence was on February 25, 2005, when I watched the first season, sixth episode, "Sabotage" of a TV show called Numb3rs. Consider yourself  warned: I "understand" math, in a wordy sort of way, and I love the concepts, but I am not a mathematician. I hope you will check out this page about the Numb3rs episode, in which Charlie, the math-geek hero, explains more about the Fibonacci sequence.

If you had to learn to read and write Roman numerals, and, as a proponent of Western culture I really hope you did, you can imagine how difficult it would be to perform simple mathematical operations like addition and multiplication without the concept of zero or the idea of a numeral for a place-holder with no value of its own.

The first known English use of the word zero was in 1598, from French zéro, Italian zero (a contraction of zefiro), and Old Spanish cefr.

I promise nothing, but, in my research, I have run into a book by Charles Seife, Zero: The Biography of a Dangerous Idea (Viking, 2000) and a Scientific American article, "The Origin of Zero," by John Matson, August 21, 2009.