semilunar valve
- noun
- /ˌsɛmɪˈlunər vælv/
- Specialized
- When the heart beats, the semilunar valve prevents the blood from flowing back inside.
Examples
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The semilunar valve opens to allow blood to flow from the heart into the aorta.
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Each semilunar valve has crescent-shaped cusps that help regulate blood flow in the heart.
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The semilunar valve should be on our left any second now.
Surface Forms
Morphology
The meaning is directly compositional: 'semilunar' = crescent/half‑moon shaped and 'valve' = a flow‑control device, so a learner who knows both constituents can infer it is a valve shaped like a crescent. The anatomical function (preventing backflow) follows from the concept of a valve, making the phrase transparent rather than idiomatic.
Etymology
Semilunar valve comes from parts that mean 'half' and 'moon': semi means 'half' and lunar means 'moon', so the valve's flaps are shaped like a half-moon. These half-moon flaps close like a 'one-way' door to stop blood from flowing back into the heart, which is why the name refers to valves that prevent backward blood flow.