Glossary
word part
A word part is a prefix, root, suffix or combining vowel — one of the pieces a medical word is built from.
A word part is one of the pieces a long medical word is assembled from — a prefix in front, a root in the middle, a suffix at the end, joined by a combining vowel where the word needs one — and the meaning is the parts combined. Pericarditis is peri- (around) plus cardi (heart) plus -itis (inflammation): inflammation around the heart. Because the root names the place and the suffix names what is happening, the fastest reading starts at the end and works backwards, suffix first, then root, then prefix. Two shapes are worth knowing. A word may have two roots and no prefix, joined by a combining vowel, and it may have a prefix with no suffix. Every part you meet on the list is also a piece of dozens of words you have not memorized, which is why the system is taught instead of the list being memorized: derive the word instead of recalling 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.
- 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.
- 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.
- position prefix — A position prefix says where something is — pre- before, post- after, sub- under, supra- above, peri- around, inter- between.
- benign — Benign describes something that is not cancerous and not harmful in itself, or a condition that runs a mild course.
- afebrile — Afebrile means without fever, and the word is built from the negation prefix a- plus febrile, meaning feverish.
- contraindication — A contraindication is a condition or circumstance in which a treatment should not be used, because its risk outweighs its benefit.
- ambulatory — Ambulatory means able to walk, or a care setting that does not require an overnight stay.
- bolus — A bolus is a single dose given quickly and in full, as opposed to the same amount delivered slowly over time; the word also names a mass of chewed food ready to be swallowed.
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)