caries

The word 'caries' was borrowed directly from the Latin noun 'cariēs', which meant 'rottenness, decay'. This Latin term is believed to derive from the Proto-Indo-European root ker-, meaning 'to injure, cut'. The semantic journey is one of metaphorical extension: from the general concept of injury or wearing away, to the specific physical process of decay in hard tissues like bone or tooth enamel. In English, it entered the medical lexicon in the 17th century and has since become the standard clinical term for tooth decay, preserving its original Latin form and singular grammatical number.

The entire word 'caries' is a simplex loanword from Latin. It functions as a singular noun in English.