Before revision: If a displacement develops perpendicular to the surface , it is called a normal tensile crack or simply a crack; if a displacement develops tangentially, it is called a shear crack, slip band or dislocation.
After revision: or somethingIf a displacement develops perpendicular to the surface , it is called a normal tensile crack or simply a crack; if a displacement develops tangentially, it is called a shear crack, slip band or dislocation.