tenacity

Synonyms: application backbone chutzpah clock courage determination doggedness firmness grit guts gutsiness guttiness heart inflexibility intestinal fortitude intransigence moxie nerve obduracy obstinacy perseverance persistence pertinacity resoluteness resolution resolve spunk starch staunchness steadfastness stick-to-itiveness stomach strength of purpose true grit what it takes willfulness

Antonyms: indifference irresolution slackness weakness