What is a carious lesion tooth and symptoms please?

A cavity: A carious lesion is the technical term for a cavity. Sensitivity to sweets would be the number 1 early symptom. Add sensitivity to cold, heat, aches, and spontaneous pain as they get larger over time. Not all cavities in the earlier stages of development produce symptoms. That's why it's important to see your dentist routinely for exams and x-rays.

Cavity: Caries is the term for a cavity. They can present as dark spots on your teeth (although not all dark spots are cavities), sensitive areas to cold and sugar, dull or acute pains. However, most of the time they have little to no symptoms at all, and must be diagnosed by a competent provider. Under the right conditions, these lesions progress very rapidly, and should be addressed asap.

Caries = decay: A carious lesion is another word for cavity or decay, and most cavities can be diagnosed (fortunately) before there are symptoms, making the treatment much simpler and less costly. Once symptoms occur (toothache, heat sensitivity, jaw pain), it will require much more involved treatment, requiring more investment than what earlier diagnosis would have allowed. See your dentist soon!