The term "caval opening" refers to an anatomical feature that serves as the passage for the vena cava, a major vein that carries deoxygenated blood from the lower half of the body to the heart. This opening is also known as the inferior vena cava hiatus and is located in the diaphragm. There are a few synonyms for this term that are commonly used in medical and anatomical contexts, including hiatus venae cavae, hiatus vena cavae, and vena cava orifice. While these synonyms may differ slightly in their terminology, they all refer to the same anatomical structure that is essential for proper blood circulation in the body.