Accuracy

In measurements accuracy is defined as the closeness with which the measured value obtained by a measuring instrument is nearer to the true value of the measuring quantity.

For example, consider measurement of 1A current with three different instruments. The true value here is 1A. If the three meters shows readings as 0.99, 0.97 and 0.98 then the first instrument is said to be highly accurate instrument among the three and the second instrument is the least accurate instrument as it shows the most difference from the true value.