firmness
n. uncountable B2 Upper Intermediate US //ˈfɝmnəs// UK //fˈɜːmnəs// firm·ness
n. the quality of being solid and hard, or the quality of being strong and not easily changed. You use this to describe how a mattress feels or how a person stands up for their beliefs.
n. the quality of being solid, hard, or resistant to pressure; also refers to the quality of being resolute or determined in one's actions or beliefs.
The mattress has a perfect level of firmness for my back.
The manager's firmness in refusing the request showed that the company's new safety rules were not to be ignored.
While the physical firmness of the leather was a testament to its quality, it was the director's moral firmness that truly defined the success of the project.
From firm + -ness.