Which prefix would you use to describe something between the ribs (intercostal)?

• A. Inter-
• B. Intra-
• C. Peri-
• D. Sub-

Answer: (A)

The concept being tested is the meaning of prefixes in medical terms, specifically how to express "between." In anatomy, intercostal describes something between the ribs. The prefix inter- comes from Latin and means between, so intercostal literally means between the ribs. The root cost means rib, giving intercostal as the space or structures located between ribs.

Other prefixes don’t fit this meaning: intra- means within, peri- means around, and sub- means under. So they would describe things inside, around, or beneath, not between. For example, the intercostal spaces and intercostal muscles are named for their position between the ribs, which is exactly what inter- conveys.