A syncytium (/sɪnˈsaɪtiəm/; plural syncytia; from Greek: σύν (syn) = "together" + κύτος (kytos) = "box, i.e. cell") is a multinucleate cell which can result from multiple cell fusions of uninuclear cells (i.e. cells with a single nucleus), in contrast to a coenocyte which can result from multiple nuclear divisions without accompanying cytokinesis. A classic example of a syncytium is the formation of skeletal muscle. The term may also refer to cells that are interconnected by specialized membrane with gap junctions, as seen in the heart muscle cells and certain smooth muscle cells, which are synchronized electrically in an action potential.
Another (correct and well established) use of the word syncytium is found in animal embryology to refer to the coenocytic blastoderm of invertebrates.