friction
  • noun a force that resists the relative motion or tendency to such motion of two bodies in contact
  • For two bodies in contact, the resistance one offers to the movement of the other relative to it. Friction may occur between solids, liquids, or gases. Friction between solids may have any of several effects, including the production of heat, wear, or electricity. With fluids, the greater the viscosity, the greater the resistance to the movement of another body through it.

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