What is the difference between these two words? They seem to mean the same thing.
A pleonasm relates to a specific word or phrase where there is redundancy (a "true fact"), whereas a tautology relates more to a logical argument or assertion being made, where it is self-evidently true (or unable to be falsified by logic), such as "I was definitely the oldest person at the meeting because everyone there was born later than me.", or "For the purpose of paying fees, the year is divided into four quarterly payments.".