Digit

A digit is a symbol used to write numbers within a particular numeral system. Its value depends on the system and, in positional notation, its place.

Numeral system: A system of symbols and rules for representing numbers. A digit’s meaning is defined by the numeral system that uses it.
Decimal system: The base-ten positional numeral system, using digits zero through nine. Its ten familiar symbols make decimal notation the common everyday example.
Number: An abstract mathematical object used to express quantity, order, or measurement. A digit is a written symbol; a number is the value its numeral can represent.
Brahmi numerals: An ancient Indian numeral system whose symbols contributed to the development of modern decimal digits. Brahmi forms are among the historical ancestors of today’s decimal symbols.
Positional notation: A numeral system in which a symbol’s value depends on its position. In positional systems, each digit’s place changes its contribution to the numeral.
Binary numeral system: The base-two positional numeral system, using only zero and one. Binary demonstrates how a small digit set can represent every whole number.
Numerical digit: A single character representing a number, especially one of the decimal symbols 0 through 9. This narrower usage often means a decimal digit rather than a system-specific symbol.
Hindu–Arabic numeral system: The decimal positional system using the digits 0 through 9, developed in India and transmitted through Arabic scholarship. Its transmission established the decimal digits now used internationally.
Place value: The value assigned to a digit by its position in a numeral. Place value explains how the same digit can represent different amounts.
Hexadecimal: The base-sixteen numeral system, commonly written with digits zero through nine and letters A through F. Its extra digit symbols compactly encode binary data.

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BaseRelated: A base has exactly that many distinct digit symbols, including zero.