What are the methods of reducing friction?/

Explanation

Following are the methods to reduce the friction.
i) Polishing the surface: Polishing the surface reduces friction because irregularities on the surface are filled on polishing.
ii) Lubrication: Lubricants like oil and grease reduces friction: By lubrication irregularities remain apart. As a result, they do not interlock tightly.
iii) By providing the streamlined shape: Bodies are made streamlined in order to reduce effect of air resistance on them.
iv) By converting sliding friction into rolling friction: Since rolling friction is much less than sliding friction, so we can reduce friction by converting sliding friction into rolling friction.