What term describes the main part of a term that contains the primary meaning?

The term that describes the main part of a term that contains the primary meaning is the word root. The word root is foundational for medical terminology as it carries the primary concept or essence of the term itself. For instance, in the term "cardiology," the root "cardio" refers to the heart, which is the core focus of the term.

Prefixes and suffixes serve different roles; a prefix is added at the beginning of a word root to modify its meaning, while a suffix is attached at the end for similar purposes, often indicating a procedure, condition, or disease. A combining form is essentially a word root combined with a vowel, used to ease pronunciation when connecting it with other word elements, but it may not convey the primary meaning in isolation. Thus, for identifying the main part that holds the primary significance, the word root is indeed the correct choice.