What term describes the process of narrowing the lumen of a vessel?

The term that describes the process of narrowing the lumen of a vessel is "restriction." In medical terminology, "restriction" is often used to refer to the constriction or narrowing of a passage or vessel, which can occur in various parts of the body, such as blood vessels or airways. This narrowing can lead to reduced blood flow or airflow, potentially causing various health concerns.

The other terms do not accurately convey the same meaning in this context. "Release" typically implies freeing or letting go of something, which does not relate to the narrowing of a vessel. "Division" suggests separating something into parts, which does not describe a constricting process. "Reduction," while it could imply a decrease, is a more general term and does not specifically capture the narrowing aspect as effectively as "restriction."