nucleus Meaning, Definition & Usage

  1. noun a part of the cell containing DNA and RNA and responsible for growth and reproduction
    karyon; cell nucleus.
  2. noun the positively charged dense center of an atom
  3. noun a small group of indispensable persons or things
    core; core group.
    • five periodicals make up the core of their publishing program
  4. 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
  5. noun any histologically identifiable mass of neural cell bodies in the brain or spinal cord
  6. noun the central structure of the lens that is surrounded by the cortex
    lens nucleus.

WordNet

Nu"cle*us noun
Etymology
L., a kernel, dim. fr. nux, nucis, nut. Cf. Newel post.
Wordforms
plural E Nucleuses L Nuclei
Definitions
  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.) (a) An incipient ovule of soft cellular tissue. (b) A whole seed, as contained within the seed coats.
  4. (Biol.) 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. it contains the genetic material, DNA ✍ 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.
  5. (Zoöl.) (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.

Webster 1913