Introduction
Definition :
Any measurement of a physical quantity is subject to an error due to the limited precision of instruments or human error. The measurement of a physical quantity can be done directly (length, temperature, time...) or indirectly for composite quantities (area, work, and moment).
Extra :
The measurement of any physical quantity can only result in an approximate value, and this is due to the following reasons: systematic errors (imperfect methods or tools) and accidental errors (operator's malfunctions[1]) which remedy by advanced devices and techniques.
Reminder :
Uncertainty in physics refers to the fact that it is impossible to measure any physical quantity with perfect precision. This is because all measuring instruments have limitations and are subject to various sources of error. For example, a ruler may not be perfectly straight, or a clock may not be perfectly accurate