Glossary
root
The root is the part of a medical word that says what the word is about — the organ, the tissue or the substance — and everything else in the word modifies it.
The root is the part of a medical word that says what the word is about — the organ, the tissue, the substance. Everything else modifies it. Card is heart, so cardiology, carditis and bradycardia are all about the heart; nephr is kidney, so nephritis is inflammation of one. A root is rarely used bare: a combining vowel, usually o, joins it to a suffix beginning with a consonant, which is why the same root appears as cardi- in carditis and cardi-o- in cardiomegaly. Two traps follow. The first is expecting one spelling per root: nephr- and ren- both name the kidney, and a word built on the second contains no trace of the first. The second is reading the vowel as part of the root rather than as the join. Read the suffix back to the root: the root tells you the subject, and the suffix tells you what is being said about it.
Taught in
Related terms
- prefix — A prefix is the part fixed to the front of a medical word, and it changes direction, size, speed, number or negation without changing what the word is about.
- suffix — A suffix is the part fixed to the end of a medical word, and it says what is being done or what kind of word this is — a condition, an inflammation, a procedure, a specialist.
- combining vowel — A combining vowel — almost always o — is the vowel placed between a root and a suffix when the suffix starts with a consonant.
- word part — A word part is a prefix, root, suffix or combining vowel — one of the pieces a medical word is built from.
Source: MedlinePlus (US National Library of Medicine) consumer guidance on understanding medical words, which the vocabulary guide follows for the prefix, root, suffix and combining-vowel system. US federal government material, not subject to copyright in the United States. Every definition and example above was written for this course in our own words; no dictionary or glossary text is reproduced. (MedlinePlus accessed 2026-10-27; definitions written 2026-10-27)