What term characterizes materials that are able to be easily scratched, indented, or penetrated?

The term that characterizes materials that are able to be easily scratched, indented, or penetrated is "soft." Soft materials typically exhibit low hardness, making them more susceptible to deformation through external forces such as scratching or indentation. This characteristic is often associated with materials like certain metals, plastics, and softer woods, which can be easily marked or shaped under pressure.

In contrast, materials described as tough have the ability to absorb energy and deform without fracturing, while hard materials resist scratching and indentation due to their high hardness levels. Rigid materials maintain their shape and resist deformation under applied stress, but this does not necessarily mean they are susceptible to scratching or indentation, as rigidity can be found in both hard and soft materials.