The nucleus, from the Latin nucleus , is the medulla, the interior, the safe, the firmness of a thing, or the central or most important part of something. In general, your term can refer to various areas.
We have that in physics and chemistry, the nucleus is the center of an atom called the atomic nucleus, a dense conglomerate of positively charged particles (protons), and which contains most of the atomic mass.
In astronomy, the nucleus is the densest and most luminous part of a star or celestial body. For example, the core of the Sun is essentially composed of hydrogen at extremely high pressure and a temperature of about 15 million degrees Celsius, where it is transformed into helium by nuclear fusion. Radiant energy passes from the core to the surface of the Sun and from there it radiates into outer space.
In the same way, in the field of geology there is the core of the Earth or terrestrial core, where it is the innermost or deepest layer of the Earth, it extends from 3000 km to the center of the planet, seismographic studies indicate that It consists of two parts: an external liquid zone, 2,220 km thick and a solid, internal zone, about 1,250 km thick. It is composed mainly of iron and other elements such as nickel, silicon and sulfur.
In the biological sphere, it is the most primordial organelle in the cell, especially the eukaryotic, known as the cell nucleus, which usually occupies the center of the cell, but this is not always the case. It also varies in shape, size and number, for example, some protozoa are plurinucleated.
The cell nucleus is surrounded by a nuclear membrane, which is nothing more than an extension of the endoplasmic reticulum. The interior of the nucleus contains a colloidal substance called nucleoplasm, in which the chromosomes and the nucleolus are embedded. The cell nucleus is considered as the molecular basis of the storage, replication and transcription of hereditary material (DNA and RNA).
Finally, in linguistics nucleus is considered as the main element in a phrase or group of words. For example, the nucleus of the noun phrase is the noun or noun, the nucleus of the verb phrase is the verb, and the prepositional phrase is the preposition, among others.
