 Hewitt–Savage zero–one law

The Hewitt-Savage zero-one law is a result in probability theory that pertains to the behavior of certain random events in a specific kind of probability space. It states that if you have a sequence of independent and identically distributed (i.i.d.) random variables, any tail event (which is an event whose occurrence or non-occurrence is not affected by the finite initial segments of the sequence) has a probability of either 0 or 1.