the quality of staying the same for a long time and not changing quickly or unexpectedly

He was unwavering in his steadfastness and devotion to science 他对科学的坚守和奉献是毫不动摇的。

Military training in steadfastness under fire is invaluable to soldiers. 针对在受到攻击的时候如何保持定力的军事训练对士兵来说极为有用。