Classify this joint by identifying the tissue that bridges the two bony pieces. Joints that use cartilage as the connecting medium fall into two groups: synchondroses (primary) are bound by hyaline cartilage, whereas symphyses (secondary) are bound by fibrocartilage. The epiphyseal growth plate is a disc of hyaline cartilage interposed between the epiphysis and metaphysis that drives the lengthwise elongation of a developing long bone. Since hyaline cartilage is the bonding tissue, the plate fits the definition of a primary cartilaginous joint, or synchondrosis, which is a temporary and essentially immovable union that disappears once skeletal growth is complete. The fibrocartilage-based alternatives such as the intervertebral disc and pubic symphysis are secondary cartilaginous joints, and a gomphosis is an entirely fibrous tooth-socket joint, so neither describes the growth plate. \[\boxed{\text{Primary cartilaginous joint}}\]