Answer:
Lubricant is used to reduce friction when replaced with fluid friction instead of sliding friction.
Explanation:
Lubricants reduce friction when replaced with fluid friction instead of sliding friction. Lubricant is used between surfaces which are in mutual contact this is used because it reduces friction between the two surfaces. Lubrication reduces heat developed in the moving parts.
This helps in removing debris from the surfaces. Mineral oils, synthetic oils, solid lubricants are used as lubricants. Lubricant acts as a 'seal' between the piston and the shaft which do not allow any gases from atmosphere.