The measurement precision of an instrument defines the smallest change in measured quantity that can be observed, which is called

Key Points

Accuracy is the ability of the instrument to measure the accurate value. In other words, it is the closeness of the measured value to a standard or true value. The accuracy can be obtained by taking small readings. 

The term precision means two or more values of the measurements are closed to each other. The value of precision differs because of the observational error. Precision is used for finding the consistency or reproducibility of the measurement. 

Resolution is the smallest amount of input signal change that the instrument can detect reliably.

The significant figures of a number are those digits that carry meaning contributing to its precision. Thus the number of significant digits depends on the least count of the measuring instrument.