What is the correct definition of the ultimate strength of a material?

The ultimate strength of a material is defined as the maximum stress it can withstand before failing. This is a critical property in materials science and engineering because it indicates the material's ability to bear loads and stresses without undergoing permanent deformation or rupture. When a material reaches its ultimate strength, it is at the brink of failure, where any additional stress can lead to fracture or significant structural compromise.

In the context of structures or components, knowing the ultimate strength helps engineers ensure safety and reliability in design by avoiding stress levels that could lead to failure. Recognizing this definition allows engineers to make informed choices about materials for different applications, taking into consideration the loads that will be applied throughout their service life.