The trea of a tire or caterpillar track refers to the rubber on its circumference that makes contact with the road. As tires are used, the tread is worn down limiting their effectiveness in providing traction. A worn tire tread can be replaced using a process known as retreading. The word tread is often used incorrectly to refer to the pattern of grooves cut into the rubber. Those grooves are correctly called the tread pattern, or simply pattern.