Precision is defined in VIM3 as the closeness of agreement between indications or measured quantity values obtained by replicate measurements on the same or similar objects under specified conditions—a crucial idea for analytical chemists. But precision as such is not quantified. Standard deviation is a quantitative concept and therefore handier in practice. But standard deviation is a measure of dispersion, which is the inverse of precision. Accordingly it is necessary in careful writing to avoid using precision as a synonym for standard deviation.