tread

Tread is a noun with several related senses. In everyday usage, it refers to the raised patterns on the surface of a material designed to provide traction or to the horizontal part of a step. As a verb, tread means to walk upon or to press with the feet.

Tire tread: The tread on motor vehicle tires is the rubber pattern that contacts the road. It channels water, provides grip, and aids braking. Tread depth is a key safety measure and varies by vehicle and climate. Depth is usually measured in millimeters or in 32nds of an inch. Worn tires can wear unevenly; wear indicators appear as small bars, and when depth reaches the minimum, the tire should be replaced. In many jurisdictions the legal minimum is 2/32 inch (about 1.6 mm). Some manufacturers recommend replacing earlier, especially for wet conditions.

Stair tread: In architecture, a stair tread is the horizontal surface a foot rests on when climbing or descending. Tread depth, or going, is measured from the nosing to the back edge, and must comply with building codes. Typical residential treads are around 10 inches (25 cm) deep, with uniform dimensions across a flight to prevent trips. The tread works with a vertical riser, and large variations can create hazards.

Other uses: The pattern on the soles of shoes or boots is also called a tread, providing traction. The verb tread also appears in phrases such as tread carefully.