The state of being invalid; lack of validity.
The result or product of being sound.
The property (of an argument) of not only being valid, but also of having true premises.
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 vDash 𝜙 must also be true, for any wff φ of logic L.
The state or quality of being sound.