What is the primary meaning of the root "vas/o"?

The root "vas/o" primarily means "vessel." In medical terminology, it is frequently used to refer to blood vessels, such as arteries and veins, as well as any tubular structures within the body. This root is derived from the Latin word "vas," which translates to "vessel."

Understanding this root helps in recognizing and forming terms related to the vasculature of the body, such as "vasodilation" (the widening of blood vessels) and "vasoconstriction" (the narrowing of blood vessels).

The other terms do not share this primary meaning. "Vein" refers specifically to a type of blood vessel, while "vagina" and "valve" refer to entirely different anatomical structures unrelated to the concept of a vessel. Therefore, "vessel" is the most accurate definition associated with the root "vas/o."