Reliability

In research, reliability means that individual scores from an instrument should be nearly the same or stable on repeated administrations of the instrument and that they should be free from sources of measurement error and consistent.

Reliability is frequently discussed together with the concept of Validity.

Source

Creswell, John W. (2011-03-14). Educational Research: Planning, Conducting, and Evaluating Quantitative and Qualitative Research (4th Edition) (Page 627). Pearson.