nucleus

noun

1. 1

   The core, central part of something, around which other elements are assembled.

2. 2

   An initial part or version that will receive additions.

   “This collection will form the nucleus of a new library.”

3. 3

   The massive, positively charged central part of an atom, made up of protons and neutrons.

4. 4

   A large membrane-enclosed organelle found in eukaryotic cells which contains genetic material.

5. 5

   A ganglion, cluster of many neuronal bodies where synapsing occurs.

6. 6

   The central part of a syllable, most commonly a vowel.