Nucleus /(?)/

pl. Nucleuses, Nuclei

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.

2. The body or the head of a comet. (Astron.)
3. An incipient ovule of soft cellular tissue. (Bot.)
4. 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. (Biol.)
5. The tip, or earliest part, of a univalve or bivalve shell. (Zool.)