Accuracy is 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).
In significance arithmetic, an approximation with estimated absolute uncertainty 
has decimal accuracy 
.
This effective measure may be negative or nonintegral; it is not a count of displayed
digits to the right of the decimal
point. For a nonzero approximation 
,
the corresponding precision is 
,
measuring relative uncertainty. Exact numbers have infinite
accuracy and precision.
