Noun, pl. nuclei
1. The core, central part (of something), round which others are assembled. (wiktionary.org)
2. An initial part or version that will receive additions. (wiktionary.org)
3. This collection will form the nucleus of a new library. (wiktionary.org)
1. The massive, positively charged central part of an atom, made up of protons and neutrons. (wiktionary.org);
2. A characteristic and stable complex of atoms or groups in a molecule (merriam-webster.com).
3. The positively charged central portion of an atom that comprises nearly all of the atomic mass and that consists of protons and neutrons except in hydrogen which consists of one proton only (merriam-webster.com).
1. A large organelle found in cells which contains genetic material (wiktionary.org).
2. Cell nucleus; a spheroid body within a cell, consisting of a thin nuclear membrane, organelles, one or more nucleoli, chromatin, linin, and nucleoplasm (medical-dictionary.thefreedictionary.com).
3. A cellular organelle of eukaryotes that is essential to cell functions (as reproduction and protein synthesis), is composed of nuclear sap and a nucleoprotein-rich network from which chromosomes and nucleoli arise, and is enclosed in a definite membrane (merriam-webster.com)
1. A ganglion, cluster of many neuronal bodies where synapsing occurs (wiktionary.org).
2. A group of nerve cells, usually within the central nervous system, bearing a direct relationship to the fibers of a particular nerve (medical-dictionary.thefreedictionary.com).
3. A mass of gray matter or group of nerve cells in the central nervous system. (merriam-webster.com)
1. The central part of a syllable, most commonly a vowel. (wiktionary.org)
Word origin: from Latin nucleus “kernel,” from nucula “little nut,” diminutive of nux (genitive nucis) “nut.”