'''Nucleus''' fundamentally means "kernel" or "central core." Nucleus is pronounced NEW-klee-us. The plural is nuclei, pronounced NEW-klee-eye. In science, this term has five main uses: | '''Nucleus''' fundamentally means "kernel" or "central core." Nucleus is pronounced NEW-klee-us. The plural is nuclei, pronounced NEW-klee-eye. In science, this term has five main uses: |