What best describes a synovial joint?

A synovial joint is characterized by having a joint cavity filled with synovial fluid, which plays a crucial role in lubricating the joint and reducing friction between the articulating surfaces of the bones. This fluid is vital for the proper functioning of the joint, as it helps nourish the cartilage and facilitates smooth movement.

Additionally, synovial joints are known for their capacity to allow a significant range of motion between connected bones, which distinguishes them from other types of joints such as fibrous or cartilaginous joints that either permit limited movement or none at all. The presence of structures like ligaments, tendons, and a joint capsule further supports the function and stability of synovial joints while allowing them to accommodate varying degrees and directions of movement.

Thus, the defining features of synovial joints: the presence of synovial fluid and their ability to permit movement, make this description the most accurate among the options provided.