Definition - What does Nucleus mean?
The term nucleus refers to an important, central part of an object, group or movement that is at the centre of its activities. It is most often used in the biological sense to refer to the central organelle found in living cells, or in physics to describe the core of an atom.
Safeopedia explains Nucleus
The importance of a nucleus (plural: nuclei) is the manner in which it controls and determines the properties of its surrounding elements. Thus, the nucleus of a living cell contains genetic material that will determine its properties and expression, and the nucleus of an atom consists of protons and neutrons that determine its atomic mass and physical properties.