from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. The nucleus of a cell
from The Century Dictionary and Cyclopedia
- n. The cell-nucleus.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. a part of the cell containing DNA and RNA and responsible for growth and reproduction
From the Ancient Greek κάρυον ("nut, kernel"). (Wiktionary)
Just a clarification: Both bacteria and archaeons are prokaryotes, so named because they lack the nucleus ( "karyon") that characterizes eukaryotes.