Tensile stress is a measure of the internal forces experienced by a material when it is stretched or pulled. It is calculated by dividing the force applied to the material by its cross-sectional area. The unit of tensile stress is typically expressed in pascals (Pa) or pounds per square inch (psi). When a material undergoes tensile stress, it may deform or elongate. If the stress exceeds the material's strength, it can lead to failure, such as breaking or yielding. Understanding tensile stress is crucial in fields like engineering and construction, where materials must withstand various forces without failing.