The prefix Spiro- denotes which morphological concept?

• A. Tube
• B. Spiral
• C. Coil
• D. String

Answer: (C)

Spiro- signals a twisting, winding form. It comes from Greek speira, meaning a coil or wound thread. Because the idea is a shape that winds or twists, the best match is coil: spiro- is used for things that are wound or twisted, capturing that winding form. A tube describes a hollow cylinder, a string implies a straight thread, and while spiral is close, spiro- emphasizes the winding/coiling quality of the shape. So the concept represented by this prefix is a coil.