| adjective | marked by firm determination or resolution; not shakable “firm convictions” |
| adjective | not showing abrupt variations; ; - Louis Auchincloss “spoke in a level voice” |
| firmness | noun | the trait of being resolute |
| steadfastness | noun | steadfast resolution |
| steadiness | noun | freedom from wavering or indecision; constancy of resolve or conduct |
| stiffness | noun | firm resoluteness in purpose or opinion or action |