As nouns the difference between firmness and steadfastness
is that firmness is the state of being firm; strength; permanence; stability; hardness; resolution while steadfastness is loyalty in the face of trouble and difficulty.
firmness
English
Noun
The state of being firm; strength; permanence; stability; hardness; resolution.
References
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steadfastness
English
Noun
Loyalty in the face of trouble and difficulty.
Steadfast resolution.