- A central or essential part around which other parts are gathered or grouped; a core: the nucleus of a city. (noun)
- Something regarded as a basis for future development and growth; a kernel: a few paintings that formed the nucleus of a great art collection. (noun)
- Biology A large, membrane-bound, usually spherical protoplasmic structure within a living cell, containing the cell's hereditary material and controlling its metabolism, growth, and reproduction. (noun)
- Botany The central kernel of a nut or seed. (noun)
- Botany The center of a starch granule. (noun)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.