It is the most superficial injury where only the upper part of the skin (epidermis) is involved.

scratch or linear abrasion

An abrasion can be a simple straight line called scratch or linear abrasion and caused by a pointed object like a metal nail or finger nail. 

grazed abrasion

When the abrasion is broad consisting of numerous parallel linear abrasions covering an area of the body is called grazed abrasion. The common cause for grazed abrasion is a fall on to the ground with a sliding movement or being hurling across a rough road surface in a traffic accident. The abrasions are important in medico legal practice as it gives several medico legal important information. 

imprint abrations

The abrasions may retain the pattern of the causative weapon and such abrasions are called imprint abrasions. The different stages of healing of abrasions cause at different time periods after the infliction of the injury and is used to determine the time of infliction. The abrasions heal in 7 to 10 days without leaving a scar.