By scientific definition, the accuracy of a measurement system is how close a result comes to the true value or a standard.
In our daily life, when we see a measurement like a speed of 25 kmph on a speedometer, or a weight of 12.2 kg on a weighing scale, we regard this value as correct without thinking about the errors those values may have. It is a common perception that ‘what we SEE is the CORRECT & ACCURATE value’.
This perception is further strengthened in today’s ‘digital’ indication age, where instruments produce a direct readout of numeric values, removing the ambiguity of analogue indication such as needle/pointer of earlier times. However the fact remains that each measurement, whether done by an analog or a digital instrument, has an error and we cannot say how accurate a measurement is unless we know the true value to compare it with.