nucleus

/ˈnukliəs/

/ˈnukliɪs/

Other forms: nuclei; nucleuses

A nucleus is often called the brain, or control center, of a eukaryotic cell (that is, a cell with a nucleus).

The noun nucleus has several senses, though most of them will appear in science. If a biology teacher says nucleus, she is probably talking about a cell (or a group of cells), but a physics teacher would be talking about the center of an atom, or possibly even the center of a comet’s head. Step out of science class, and nucleus likely refers to a core group — like the math fanatics that math club could not function without.

Definitions of nucleus

1. noun

   a part of the cell containing DNA and RNA and responsible for growth and reproduction
   synonyms: cell nucleus, karyon

   types:

   pronucleus

   the nucleus of the ovum or sperm after fertilization but before they fuse to form the nucleus of the zygote

   subthalamic nucleus

   an oval mass of grey matter located in the caudal part of the subthalamus; associated with the striate body

   type of:

   cell organ, cell organelle, organelle

   a specialized part of a cell; analogous to an organ
2. noun

   the positively charged dense center of an atom
   type of:

   center, centre, midpoint

   a point equidistant from the ends of a line or the extremities of a figure
3. noun

   a small group of indispensable persons or things
   synonyms: core, core group

   types:

   cadre

   a nucleus of military personnel capable of expansion

   type of:

   set

   a group of things of the same kind that belong together and are so used
4. noun

   any histologically identifiable mass of neural cell bodies in the brain or spinal cord
   types:

   dentate nucleus

   a large laminar nucleus of grey matter within the white matter of each cerebral hemisphere

   type of:

   neural structure

   a structure that is part of the nervous system
5. noun

   the central structure of the lens that is surrounded by the cortex
   synonyms: lens nucleus

   type of:

   anatomical structure, bodily structure, body structure, complex body part, structure

   a particular complex anatomical part of a living thing
6. 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
   type of:

   center, centre, midpoint

   a point equidistant from the ends of a line or the extremities of a figure