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*Definition: definition*

- A statement that introduces into a theory a new constant and additional axioms.
- Restriction: no formula can be derived in new theory that could not be
derived from orginal theory (
*consistency*).

*Example*: Real Numbers

- Unary function constant | |.
**forall**`x`: 0 <=`x`=> |`x`| =`x`**forall**`x`:`x`<=`0`=> |`x`| = -`x`

Author: Wolfgang Schreiner

Last Modification: October 14, 1999