In physics and engineering, measurement is the activity of comparing physical quantities of real-world objects and events. Established standard objects and events are used as units, and the measurement results in a given number for the relationship between the item under study and the referenced unit of measurement. Measuring instruments are the means by which this translation is made.
Physicists use a vast range of instruments to perform their measurements. These range from simple objects such as rulers and stopwatches to electron microscopes and particle accelerators.
