Precision is the extent of detail (or "exactness") used in expressing a number. Precision is specified as the number of significant digits (or the number of decimal places) with which a quantity is reliably expressed and can be repeatedly expressed. For example, the value of pi (, the circumference of a circle divided by that circle's diameter) is expressed with more precision when pi's value is stated as 3.14159285, rather than when pi is expressed as 3.14. Precision is related to, but different from, accuracy. Precision indicates "degree" of detail, while accuracy indicates "correctness" of detail. That is, accuracy involves how close to the real value a measurement is, or the degree to which the result of a calculation or measurement approximates the true value. Therefore, a value of pi stated as 3.14159285 has both more precision and more accuracy than a value of pi stated as 3.14 because it has more digits...