A measure of the precision with which a value has been obtained from a series of measurements. For example, the parallax, π‎, of a star may be given as π‎ = 0″.096 ± 0″.003. Here, 0″.096 is the value and 0″.003 is the probable error. It means that the probability that the true value of π‎ lies between 0″.093 and 0″.099 is equal to the probability that it lies outside the range 0″.093 to 0″.099.