1. A list of materials which produce an electrostatic charge when rubbed together, arranged in such an order that a material has a positive charge when rubbed with a material below it in the list, and has a negative charge when rubbed with a material above it in the list.
2. A type of contact electrification in which certain materials become electrically charged after they come into contact with a different material and are then separated by rubbing.

The polarity and strength of the charges which are produced are determined by the materials, surface roughness, temperature, and other characteristics.