The word root of the medical term thoracic is:

The term "thoracic" is derived from the word root "thorac," which pertains to the thorax or chest area of the body. In medical terminology, the root of a word typically provides the central meaning, and understanding this root is essential for interpreting and constructing medical terms. The thorax encompasses structures such as the rib cage, lungs, and heart.

Recognizing "thorac" as the root allows healthcare professionals and nursing assistants to effectively communicate regarding conditions, procedures, and anatomy associated with the chest region. Other options do not represent any standard medical roots, making them unrelated to the term in question. Therefore, the identification of "thorac" as the base for "thoracic" deepens your understanding of the language used in healthcare settings.