What is a combining form?

A combining form is indeed defined as a root word with an added vowel, specifically the letter "o" most commonly, that allows it to connect with other words or combining forms. This structure is essential in medical terminology, as it enables the formation of complex terms that describe medical conditions, procedures, or anatomy by combining different root words into a more comprehensive whole. For example, "cardi/o", which refers to the heart, can be combined with other terms such as "cardiology" (the study of the heart) or "cardiogram" (a recording of heart activity).

The other options do not accurately define a combining form. A compound word typically consists of two complete words rather than a root and a vowel. Synonyms relate to similar meanings and do not pertain to the structure of words in medical terminology. A suffix modifies the meaning of a root word but does not form the connecting structure characteristic of a combining form. Thus, the emphasis on the combination of root words with added vowels distinguishes the correct definition of a combining form in medical language.