Precision in pipetting refers to the ability of a pipette to consistently and accurately measure and transfer a specific volume of liquid. A pipette is considered to be precise if, when measuring and transferring the same volume of liquid multiple times, the volumes obtained are very similar to one another. Pipettes are precision instruments and have a small measurement uncertainty, which is usually specified in terms of the standard deviation of a sample of repeated measurements of the same volume, called the precision error. The precision error of a pipette is usually measured and specified by the manufacturer, or it can be determined by lab calibration. Precision is an important aspect of pipetting because accurate results depend on precise measurement of the liquid volumes. For example, in experiments where reproducibility is a key factor, precise pipetting is necessary to ensure that the same volume of liquid is used each time. In addition, in analytical chemistry, where very small volumes of liquid are often used, precise pipetting is necessary to ensure accurate results. However, precision alone is not enough to guarantee the accuracy of the measurement. Pipettes, like any measurement instruments, also have an inherent systematic error, called the accuracy error. This type of error is usually determined by using a reference standard that is traceable to a national or international standard. To guarantee accurate measurement, both precision and accuracy should be considered and controlled. This can be done through regular calibration, proper maintenance and use of pipettes, and using the correct technique when pipetting.