#### Answer

The base in the Hindu-Arabic numeration system is 10. Therefore, the positional value of Arabic numeration system is based on powers of 10 then the positional values of this system are\[.....,{{10}^{3}},{{10}^{2}},10,1\].
For example, a Hindu-Arabic numeral 122 represented in expanded form on base 10 as below,
\[122=\left( 1\times {{10}^{2}} \right)+\left( 2\times {{10}^{1}} \right)+\left( 2\times 1 \right)\]
And, the symbols which represent a Hindu-Arabic numeral is called digit. So, the ten symbols 0,1,2, 3,4,5,6,7,8,9 is called digit for Hindu-Arabic numeration system.