What term refers to a soft decayed area in a tooth?

The term that refers to a soft decayed area in a tooth is "caries." This term is commonly used in dentistry to describe tooth decay or cavities, which result from the demineralization of tooth structure due to the activity of bacteria feeding on sugars in the mouth. Caries can lead to pain, infection, and further deterioration if not treated. It is essential for dental professionals to identify and manage caries early to prevent complications.

The other choices do not pertain to dental issues. The cerebellum is part of the brain responsible for motor control, conjunctivitis is an inflammation of the conjunctiva in the eye, and diabetes mellitus is a metabolic disorder that affects blood sugar levels, none of which relate to tooth decay.