drag; fluid resistance — the force opposing motion of an object through a fluid (air or water).
飛行機は抗力を減らすために流線形に設計されている。
Aircraft are designed with streamlined shapes to reduce drag.
自転車の速度が上がると、抗力も大きくなる。
As the bicycle's speed increases, the drag also increases.
a (surface) reaction force — sometimes used to mean the reaction forces acting on a surface (normal force or frictional force).
箱を押すと床から抗力が働き、摩擦のために動きにくくなる。
When you push the box, a reaction force from the floor acts and friction makes it hard to move.
斜面では重力と抗力の釣り合いを考えて運動を解析する。
On an incline, motion is analyzed by considering the balance between gravity and reaction (resisting) forces.