(n.) Quality of being sturdy.

body concreteness decisiveness density durability endurance energy firmness force fortitude guts gutsiness hardiness hardness heartiness intestinal fortitude lustihood lustiness mass materiality might mightiness obstinacy palpability ponderability potency power powerfulness robustness ruggedness solidity soundness stability stalwartness stamina staunchness staying power steadiness sticking power stoutness strength strength of will substance substantiality substantialness tangibility temper toughness vigor vigorousness vitality