A denary number is a number in the base 10, or decimal, system. Most of the numbers used internationally are denary numbers, with a few exceptions possible in specific fields such as computer science.
Numerals

The base of a numeral system refers to the number of numerals that are used for expressing a number in that system. Denary numbers use 10 numerals. These are "0," "1," "2," "3," "4," "5," "6," "7," "8" and "9."
Place Value

Digits in denary numbers have a place value given by their position within the number. If there is no decimal point, the rightmost digit is in the "ones" place, which has the value of the digit times 10^0 (10 raised to the zeroth power, or 1)..
Fractional Values

Digits to the right of the decimal point in denary numbers show portions of a whole. The value of each digit is determined by its place. The value of the first digit to the right of the decimal point is the digit multiplied by 10^(1), or 1/10. Each digit to the right of the decimal point has a value of the digit multiplied by 10^(n), where "n" stands for the number of places to the right of the decimal point.
Identification

Base 10 is the common numeral system used internationally. Unless otherwise specified, a number can be assumed to be denary.
Other Base Systems

Besides base 10 numeral system, computer scientists may use base 2 (binary), base 8 (octal) and base 16 (hexadecimal) numeral systems.