Learner's definition of INERTIA
[noncount]
1
a : lack of movement or activity especially when movement or activity is wanted or needed缺乏活力 b : a feeling of not having the energy or desire that is needed to move, change, etc.惰性 2
physics : a property of matter by which something that is not moving remains still and something that is moving goes at the same speed and in the same direction until another thing or force affects it惯性
— inertial
/ɪˈnɚʃəl/ adjective, physics