(n.) The quality of being invariable; invariableness; constancy; uniformity.

assurance balance balanced personality composure confidence constancy constraint control cool coolness discipline ease easiness equability equanimity equilibrium erectness fastness firmness homeostasis imperturbability independence invariability level head levelheadedness nerve nonchalance orthogonality perpendicularity plumbness plungingness poise possession precipitousness presence of mind reliability restraint right-angledness right-angularity rootedness sang-froid sangfroid savoir faire secureness security self-assurance self-command self-confidence self-conquest self-control self-denial self-discipline self-government self-mastery self-possession self-restraint sheerness solidity soundness squareness stability stable equilibrium stable state steadfastness steadiness steady nerves steady state steepness substantiality undeflectability uniformity unshakable nerves unshakableness up-and-downness uprightness verticalism verticality verticalness well-regulated mind