Which term describes a force that opposes motion between two surfaces in contact?

Friction is the term that describes a force that opposes the motion between two surfaces in contact. When two surfaces rub against each other, friction acts in the opposite direction of the movement, resisting the sliding or movement. This force can vary in strength depending on the nature of the surfaces (such as roughness or smoothness) and the amount of force pressing them together. Friction is essential in everyday life, as it allows us to walk without slipping and helps vehicles gain traction on the road.

The other terms listed involve different concepts: inertia refers to the tendency of an object to resist changes in its state of motion; drag is a force that opposes motion through a fluid (like air or water); and momentum is the quantity of motion an object possesses, dependent on its mass and velocity. Each of these terms describes different physical phenomena, but none pertains to the specific interaction of opposing forces between two surfaces in contact like friction does.