1.  sturdiness(n = noun.state) - the state of being vigorous and robust;
is a kind of good health, healthiness
Derived form adjective sturdy₁

2.  sturdiness(n = noun.attribute) - the property of something that is strongly built;
is a kind of strength
Derived form adjective sturdy₃

3.  sturdiness(n = noun.attribute) - resoluteness evidenced by strength of character; "sturdiness of moral principle"
is a kind of firmness, firmness of purpose, resoluteness, resolution, resolve
Derived form adjective sturdy₂

   Quality of being sturdy. [1913 Webster]