Lubricant

A lubricant is a substance introduced between two surfaces to lessen the friction between them. Lubricants have been used since prehistoric times, for example on wheel axles, and see extended use in many industrial applications.

Common lubricants include:

• Petroleum-based oils.
• Vegetable fat-based oils.
• Animal fats, e.g. lard.
• Grease.
• K-Y jelly, often used as a medical and sexual lubricant.
• Dry graphite powder.
• Teflon tape used in plumbing.
• PTFE powder.

Another way to reduce friction is to use a ball bearing, which at the time of its invention was revolutionary. An air cushion can also be used to reduce friction.