Friction . is a force which works in the opposite direction of motion
was first proposed by Sir Isaac Newton
is the reason work output is always greater than work input
works in the same direction as motion

is a force which works in the opposite direction of motion

Explanation:

Friction is a force between two surfaces that are sliding, or trying to slide, across each other. For example, when you try to push a book along the floor, friction makes this difficult. Friction always works in the direction opposite to the direction in which the object is moving, or trying to move.