A convergence rate describes how quickly an estimator or sequence approaches its limiting or expected value as sample size n increases. For sequences of the form 1/n^a, larger positive a means faster convergence. section 8.1.2
Comparing 1/n and 1/√n
Both 1/n and 1/√n approach zero, but 1/n does so faster. A root-n consistent estimator approaches its expected value at rate 1/√n. The sample mean has this rate under the central limit theorem, and Double Machine Learning is proved to have it under stated assumptions. section 8.1.2
