1.) a. Needless repetition of the same sense in different words; redundancy.
b. An instance of such repetition.
2.) Logic. An empty or vacuous statement composed of simpler statements in a fashion that makes it logically true whether the simpler statements are factually true or false; for example, the statement "Either it will rain tomorrow or it will not rain tomorrow."
Not to be confounded with the oxymoron or the paradox, the logical anomaly known as the tautology is a fascinating phenomenon.
Perhaps one of the most interesting tautologies are those that transcend languages or are resultants of linguistic misinterpretation:
1.) Pomodoro tomato is literally, translated as a redundancy,
tomato tomato/pomodoro pomodoro.
2.) Manos: The Hand of Fate (fr. wikipedia)
Interesting also is the temporal tautology, which would be redundant based on one's context either historically or chronologically.
Siam Thai, a restaurant in San Francisco. Two places which are literally the same place, but at different times in history.
Istanbul, not Constantinople...except when it was Constantinople, after having been Istanbul originally; but it hasn't always been Istanbul, either. Essentially, it is both places because it has been both places...perhaps a technicality, but it is technically true.
Let's dispense with Yogi Berra's redundant witticisms...need I say more than the fact that they have been said?