Nucleus

1. A whole seed, as contained within the seed coats.
2. A visceral mass, containing the stomach and other organs, in Tunicata and some mollusks.
3. The tip, or earliest part, of a univalve or bivalve shell.
4. 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.
5. 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.
6. An incipient ovule of soft cellular tissue.
7. The body or the head of a comet.
8. The central part around which additional growths are added, as of an operculum.