## TAUTOLOGY

### Tautology

In logic, a tautology is a formula which is true in every possible interpretation. Philosopher Ludwig Wittgenstein first applied the term to redundancies of propositional logic in 1921; it had been used earlier to refer to rhetorical tautologies, and continues to be used in that alternate sense.

The above text is a snippet from Wikipedia: Tautology (logic)

### tautology

#### Noun

1. redundant use of words
It is tautology to say, "Forward Planning".
2. An expression that features tautology.
''The expression "raze to the ground" is a tautology, since the word "raze" includes the notion "to the ground".
3. A statement that is true for all values of its variables
Given a Boolean A, "A OR (NOT A)" is a tautology.
A logical statement which is neither a tautology nor a contradiction is a contingency.
A tautology can be verified by constructing a truth tree for its negation: if all of the leaf nodes of such truth tree end in X's, then the original (pre-negated) formula is a tautology.

The above text is a snippet from Wiktionary: tautology