Medical Terminology
Decode clinical language one meaningful piece at a time.
Lesson 4 of 12
Prefixes: number, position, and direction
Prefixes can describe how many, where, or in which direction. Number prefixes help quantify anatomy or activity, while positional prefixes locate something relative to another structure. Directional prefixes can describe movement toward or away from a reference point. Interpret these clues as part of the term, not as a substitute for anatomical orientation.
Key points
- mono- and uni- suggest one; bi- suggests two.
- tri- means three and poly- indicates many or much.
- endo- means within; ecto- and exo- suggest outside or outward.
- inter- means between; intra- means within.
- peri- means around, while sub- generally means under or below.
- A prefix may have context-dependent nuances; verify the whole word.
Key terms
- mono-
- One or single.
- bi-
- Two or twice.
- poly-
- Many or much.
- endo-
- Within or inside.
- inter-
- Between.
- intra-
- Within.
- peri-
- Around.
Memory tip
Contrast inter- (between) with intra- (within) aloud.
Clinical note
Prefixes do not always map one-to-one to everyday English or Spanish.
Unit checkpoint
Lock it in: match the terms, then test yourself.