The state or quality of being firm.

the quality of being steady or securely and immovably fixed in place

A sought after quality, usually interpreted to mean support. Firmness for some is a comfort term synonymous with hardness, for others it is a structural term associated with the support of the innerspring unit.

the firmness and tone of healthy tissue; "his muscle firmness"

the skin losses its firmness due to aging although it can also disappear prematurely due to other reasons (pregnancy, a sedentary lifestyle). To recover skin firmness, from a mechanical point of view, it is possible to recur to physical exercise or massaging. In the first case, muscle mass is tonified, which in turn tenses other tissues. Whereas with a massage, an increase in blood and lymphatic circulation is also achieved.

Firmness is a faculty from the discipline of Phrenology.

the property of being unyielding to the touch

the trait of being resolute; firmness of purpose; "his resoluteness carried him through the battle"; "it was his unshakeable resolution to finish the work"