nucleus

n. kernel, central and most significant part of a whole; positively charged heart of an atom (Physics); core of a cell containing DNA and RNA (Biology); core of the head of a comet (Astronomy)

Nucleus may refer to: In physics:Atomic nucleus, the collection of protons and neutrons in the center of an atom, also composed of subatomic matterIce nucleus, the center of an ice crystalCloud condensation nuclei, the basis for the development of a cloud dropletIn biology:Cell nucleus, the control center of a cell, which contains the cell's chromosomal DNANucleus (neuroanatomy), a central nervous system structure composed mainly of gray matterIn astronomy:Comet nucleus, the solid core of a cometGalaxy nucleus, the central region of a galaxy
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Noun
1. a part of the cell containing DNA and RNA and responsible for growth and reproduction
(synonym) cell nucleus, karyon
(hypernym) organelle, cell organ
(hyponym) pronucleus
(part-holonym) cell
(substance-meronym) nucleoplasm, karyoplasm
(part-meronym) nucleolus, nucleole
(derivation) nucleate
2. the positively charged dense center of an atom
(hypernym) center, centre, midpoint
(part-holonym) atom
(part-meronym) nucleon
3. a small group of indispensable persons or things; "five periodicals make up the core of their publishing program"
(synonym) core, core group
(hypernym) set
(hyponym) cadre
4. (astronomy) the center of the head of a comet; consists of small solid particles of ice and frozen gas that vaporizes on approaching the sun to form the coma and tail
(hypernym) center, centre, midpoint
(part-holonym) comet
(classification) astronomy, uranology
5. any histologically identifiable mass of neural cell bodies in the brain or spinal cord
(hypernym) neural structure
(hyponym) dentate nucleus

(n.)
The tip, or earliest part, of a univalve or bivalve shell.
  

(n.)
The central part around which additional growths are added, as of an operculum.
  

(n.)
The body or the head of a comet.
  

(n.)
An incipient ovule of soft cellular tissue.
  

(n.)
A whole seed, as contained within the seed coats.
  

(n.)
A visceral mass, containing the stomach and other organs, in Tunicata and some mollusks.
  

(n.)
A kernel; hence, a central mass or point about which matter is gathered, or to which accretion is made; the central or material portion; -- used both literally and figuratively.
  

(n.)
A body, usually spheroidal, in a cell or a protozoan, distinguished from the surrounding protoplasm by a difference in refrangibility and in behavior towards chemical reagents. It is more or less protoplasmic, and consists of a clear fluid (achromatin) through which extends a network of fibers (chromatin) in which may be suspended a second rounded body, the nucleolus (see Nucleoplasm). See Cell division, under Division.
  

In cell biology, the structure that houses the chromosomes. In neuroanatomy, a group of nerve cells.