Standard error is a statistical term that refers to the standard deviation of a sampling distribution. It measures the variability of a sample's mean from the population mean. In other words, standard error indicates how far the sample mean is likely to be from the true population mean. There are several synonyms for standard error, including standard deviation of the sample mean, standard deviation of the sampling distribution, standard error of the estimate, and standard error of measurement. These terms are used interchangeably and refer to the same concept in different contexts. Standard error is an essential measure of uncertainty in statistical analysis that is critical in decision making.