What term best describes the degradation of a material's strength or quality over time?

The term that best describes the degradation of a material's strength or quality over time is "deterioration." Deterioration refers to the process through which a material's properties decline due to various factors such as environmental conditions, chemical exposure, fatigue, or general wear and tear. This term encompasses a range of physical changes, including loss of strength, degradation of appearance, and reduced functionality, all of which occur progressively over time.

In contrast, "deflation" is generally used in the context of economics to describe a decrease in the general price level of goods and services, rather than a change in material characteristics. "Deformation" refers to the change in shape or size of a material when subjected to stress, which may not necessarily imply a loss of quality or strength over time. Lastly, "delamination" specifically describes the separation of layers in a laminated material, which is a type of failure but does not encompass the broader concept of overall material degradation. Therefore, "deterioration" is the most appropriate term for the decline in a material's quality or strength over time.