The term synovial refers to a type of joint in which there is a fluid-filled cavity that lubricates and reduces friction between bones. This type of joint allows for greater flexibility, mobility, and ease of movement compared to other types of joints such as hinge or pivot joints. Synovial joints are the most common type of joint in the human body and include ball-and-socket, saddle, pivot, and gliding joints among others. The fluid within the synovial cavity is called synovium, which helps to nourish and protect the joint tissues.