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:
In biology, the region of a eukaryotic cell about 10 - 20 nanometres in diameter which usually looks dark and round under the microscope. It was identified and given the name long before it was discovered that it contains the chromosomes, which contain the cell's DNA.
In meteorology, the tiny grains of dust which induce water vapor to condense out into raindrops or snowflakes;
In medicine, some parts of the brain are called nuclei; for example, the nucleus caudatus.
- Wile, Dr. Jay L. Exploring Creation With Biology. Apologia Educational Ministries, Inc. 1998