assurance, audacity, brashness, bulldog courage, cohesiveness, decisiveness, durability, endurance, energy, force, fortitude, gameness, gaminess, grittiness, guts, gutsiness, haleness, hardihood, hardness, heartiness, infrangibility, intestinal fortitude, lastingness, leatherlikeness, longevity, lustihood, lustiness, mettlesomeness, might, mightiness, nerve, nerviness, obstinacy, pertinaciousness, pertinacity, pluckiness, potency, power, powerfulness, resistance, resoluteness, resolution, robustness, ropiness, ruggedness, spunkiness, stalwartness, stamina, staying power, sticking power, stiffness, stoutness, strength, strength of will, stringiness, stubbornness, sturdiness, tenaciousness, tenacity, toughness, unbreakability, unbreakableness, vigor, vigorousness, viscidity, vitality