The Collaborative International Dictionary of English v.0.48:
Nucleus \Nu"cle*us\, n.; pl. E. Nucleuses, L. Nuclei. [L., a
kernel, dim. fr. nux, nucis, nut. Cf. Newel post.]
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
It must contain within itself a nucleus of truth.
2. (Astron.) The body or the head of a comet.
(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 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.
(a) The tip, or earliest part, of a univalve or bivalve
(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.