'Nucleus' definitions:

Definition of 'nucleus'

(from WordNet)
noun
A part of the cell containing DNA and RNA and responsible for growth and reproduction [syn: nucleus, cell nucleus, karyon]
noun
The positively charged dense center of an atom
noun
A small group of indispensable persons or things; "five periodicals make up the core of their publishing program" [syn: core, nucleus, core group]
noun
(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
noun
Any histologically identifiable mass of neural cell bodies in the brain or spinal cord
noun
The central structure of the lens that is surrounded by the cortex [syn: lens nucleus, nucleus]

Definition of 'Nucleus'

From: GCIDE
  • Nucleus \Nu"cle*us\, n.; pl. E. Nucleuses, L. Nuclei. [L., a kernel, dim. fr. nux, nucis, nut. Cf. Newel post.] [1913 Webster]
  • 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. [1913 Webster]
  • It must contain within itself a nucleus of truth. --I. Taylor. [1913 Webster]
  • 2. (Astron.) The body or the head of a comet. [1913 Webster]
  • 3. (Bot.) (a) An incipient ovule of soft cellular tissue. (b) A whole seed, as contained within the seed coats. [1913 Webster]
  • 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. [1913 Webster +PJC]
  • Note: The nucleus is sometimes termed the endoplast or endoblast, and in the protozoa is supposed to be concerned in the female part of the reproductive process. See Karyokinesis. [1913 Webster]
  • 5. (Zool.) (a) The tip, or earliest part, of a univalve or bivalve shell. (b) The central part around which additional growths are added, as of an operculum. (c) A visceral mass, containing the stomach and other organs, in Tunicata and some mollusks. [1913 Webster]