Is There a Difference Between Tautology and Pleonasm?

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 ...

Is tuna fish a tautology?

This sentence contains four tautologies: 'cooked and prepared' mean the same thing in this sentence, 'deliciously tasty' says the same thing twice, 'also' makes 'as well' grammatically redundant, and 'tuna fish' is a popular tautology that's no different than saying just 'tuna.

What is an example of pleonasm?

For example, “I like a smuggler. He is the only honest thief.” However, pleonasm is a combination of two or more words which are more than those required for clear expression. For example, “I saw it with my own eyes.”