An Arabic numeral is one of the ten digits 0, 1, 2, 3, 4, 5, 6, 7, 8, and 9. The names "Hindu-Arabic numerals" and "Indo-Arabic numerals" are also used, emphasizing the Indian origins and transmission through Arabic scholarship to Europe (Smith and Karpinski 1911, Petrocchi 2019). "Arabic numerals" remains a conventional name and does not imply that the symbols originated in Arabia.
The digits should be distinguished from the decimal numeral system, which combines them using place value. In this base-10 system, the value contributed by a digit depends on its position, and zero serves as a placeholder. For example,
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The zero distinguishes 205 from 25 without changing the shapes of the other digits. Other regional forms of the digits can be used with the same decimal place-value principle (Smith and Karpinski 1911).
The Indian decimal place-value system had reached Baghdad by the ninth century, and forms of the nine nonzero digits appear in the Spanish Codex Vigilanus of 976 (Petrocchi 2019). Adoption in Europe was gradual. Fibonacci's Liber abaci, first composed in 1202 and revised in 1228, helped disseminate the system (Petrocchi 2019). Fibonacci described his education in the following passage, quoted by O'Connor and Robertson (2001): "When my father, who had been appointed by his country as public notary in the customs at Bugia acting for the Pisan merchants going there, was in charge, he summoned me to him while I was still a child, and having an eye to usefulness and future convenience, desired me to stay there and receive instruction in the school of accounting. There, when I had been introduced to the art of the Indians' nine symbols through remarkable teaching, knowledge of the art very soon pleased me above all else and I came to understand it, for whatever was studied by the art in Egypt, Syria, Greece, Sicily, and Provence, in all its various forms."
