Syncytium refers to a single cell or cytoplasmic mass containing several nuclei by fusion of cells or by division of nuclei.
When karyokinesis is not followed by the process of cytokinesis or when nucleus division is not followed by cell division, a multinucleate condition occurs. These leads to the formation of syncytium.
Hence, syncytium is formed as result of absence of cytokinesis after karyokinesis.