Lubricant

A lubricant is a substance introduced between to surfaces to lessen the friction between them. Lubricants has been used since prehistoric times for example on [wheel axel]?s, and see extended use in many industrial applications.

Common lubricants include:

• Petroleum based oils.
• Vegetable fat based oils.

Another way to reduce friction is the use off [ball bearing]?s, which at the time of its invention was revolutionary.