Nucleus

Nu´cle`us

n.	1.
	1.	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. It must contain within itself a nucleus of truth. - I. Taylor.
	2.	(Astron.) The body or the head of a comet.
	3.	(Bot.) An incipient ovule of soft cellular tissue.
	4.	(Biol.) A body, usually spheroidal, in a eukaryotic cell, distinguished from the surrounding protoplasm by a difference in refrangibility and in behavior towards chemical reagents, which contains the chromosomal genetic material, including the chromosomal DNA. 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.
	5.	(Zool.) The tip, or earliest part, of a univalve or bivalve shell.

Noun	1.	nucleus - a part of the cell containing DNA and RNA and responsible for growth and reproduction Synonyms: cell nucleus, karyon
	2.	nucleus - the positively charged dense center of an atom
	3.	nucleus - a small group of indispensable persons or things; "five periodicals make up the core of their publishing program" Synonyms: core group, core
	4.	nucleus - (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
	5.	nucleus - any histologically identifiable mass of neural cell bodies in the brain or spinal cord