The prefix hydro- refers to which?

• A. Water
• B. Moisture
• C. Tissue
• D. Blood

Answer: (A)

Hydro- denotes water. It comes from the Greek word for water, hydor, and is used in medical and scientific terms to indicate a relationship to water. You’ll see it in words like hydrotherapy (therapy using water), hydrocephalus (accumulation of fluid in the brain), and hydrolysis (chemical breakdown by water). Moisture is a general dampness and isn’t a formal prefix, while tissue and blood don’t inherently convey a water relationship, so they don’t fit with hydro-. Water is the underlying meaning here.