In a radioactive decay chain, what is the name of the special balance reached when the rate at which a short-lived 'child' isotope is created equals the rate at which it disappears?

The special balance reached in a radioactive decay chain, when the rate at which a short-lived 'child' isotope is created equals the rate at which it disappears, is known as radioactive equilibrium. This phenomenon occurs within a radioactive decay chain, which is a sequence of nuclear transformations where an unstable atomic nucleus, called a 'parent' isotope, decays into another, often also unstable, 'child' isotope. An isotope refers to atoms of the same chemical element that have the same number of protons but different numbers of neutrons. The 'rate' of creation or disappearance refers to the number of atoms decaying or being formed per unit of time, also known as activity. The time it takes for half of the radioactive atoms in a sample to decay is called its half-life. There are two primary types of radioactive equilibrium, distinguished by the relative half-lives of ....