Final answer:
Brittleness is the characteristic of a material that causes it to break with little to no deformation prior to fracturing, whereas tensile strength is all about the stress level that leads to permanent deformation or fracture of a material.
Step-by-step explanation:
The ability of a material to break without much deformation occurring before fracture is known as brittleness. When a brittle material is subjected to stress, it does not undergo significant plastic deformation before breaking; it fractures almost immediately after the elastic limit is exceeded. Ductile materials, in contrast, undergo significant plastic deformation, with a gradual decrease in stress as strain increases, before finally reaching the breaking point. Tensile strength is the breaking stress that will cause permanent deformation or fracture of a material.