IPA: //ʌnˈsaʊndnəs//
KK: /ʌnˈsaʊndnəs/
The condition of not being in good health or not being reliable or safe.
The unsoundness of the building's structure raised concerns about its safety.
Unsoundness → It is formed from "un-" (meaning not) and "sound" (from Old English *sund*, meaning healthy or safe) and "-ness" (meaning the state of). The word "unsoundness" refers to the state of being not healthy or not safe.
Think of 'not' ('un-') being added to 'healthy' ('sound') to remember that 'unsoundness' means the state of being unhealthy or unsafe.