From Middle English soundenes, soundnes, from Old English *sundnes, *ġesundnes (attested in onsundnes), from Proto-West Germanic *sundnassī (“soundness, health”); equivalent to sound + -ness. Cognate with West Frisian sûnens (“soundness, health”), Middle Low German suntnisse (“soundness, health”), Middle High German suntnisse (“soundness, health”), German Gesundnis (“health”).
- (uncountable) The state or quality of being sound.
- (countable) The result or product of being sound.
- (logic) The property (of an argument) of not only being valid, but also of having true premises.
- (logic) 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 is true, then must also be true, for any wff φ of logic L.
- 1611, The Holy Bible, […] (King James Version), London: […] Robert Barker, […], OCLC 964384981, Isaiah 1:6:
- From the ſole of the foote, euen vnto the head, there is no ſoundnesse in it; but wounds, and bruises, and putrifying ſores: they haue not beene closed, neither bound vp, neither mollified with oyntment.