The degree to which a given quantity is correct and free from error. For example, a quantity specified as 
has an (absolute) accuracy of 
(meaning its true value can fall in the range 99-101), while a quantity specified
as 
has a (relative) accuracy of
(meaning its true value can fall
in the range 98-102).
The concepts of accuracy and precision are both closely related and often confused. While the accuracy of a number 
is given by the number of significant decimal (or other) digits
to the right of the decimal point in 
, the precision of 
is the total number of significant decimal (or other) digits.
