What does intra- mean?

• A. Within, Inside
• B. Under, Below
• C. Nose
• D. Stone, Calculus

Answer: (A)

Intra- means inside or within. It’s a prefix used to show that something is located inside a space, cavity, or structure, such as intramuscular (inside a muscle) or intracranial (inside the skull), or intravenous (inside a vein). That’s why “within, inside” is the best way to understand this prefix. Other ideas point to different prefixes: under or below would use a prefix like sub-, the nose would be indicated by naso- or rhino-, and stone/calculus relates to litho- or calculus terms, none of which convey the inside-within sense of intra-.