soundness

Short definition from Wiktionary

Noun

1. 1
   The state or quality of being sound.
2. 2
   The result or product of being sound.
3. 3
   The property (of an argument) of not only being valid, but also of having true premises.
4. 4
   The property of a logical theory that whenever a wff is a theorem then it must also be valid. Symbolically, letting T represent a theory within logic L, this can be represented as the property that whenever T⊢φ is true, then T⊨φ must also be true, for any wff φ of logic L.