Nucleus

Part of speech: noun

Pronunciation: /ˈnjuː.kli.əs/

Definitions

1. A dense central mass found within atoms and cells, or the vital centerpiece from which a larger structure or system grows
2. The central region within an atom containing protons and neutrons ; the membrane-bound organelle in a cell that contains genetic material ; the main or essential core around which something is organized or developed
3. A dense center inside an atom made up of protons and neutrons ; the part of a cell housing chromosomes and controlling functions ; the focal or key element that serves as the backbone of a structure or activity

Etymology: Before it named the heart of an atom, "nucleus" meant the kernel inside a nut or seed. The Latin "nux" meant "nut," and "nucleus" was a diminutive of it, a little nut or the kernel within. English borrowed the word directly from Latin as a learned term, and the earliest recorded English senses were quite ordinary: the head of a comet and the kernel of a seed, both noted in the 1704 "Lexicon Technicum." The atomic sense came much later. In 1844 the British scientist Michael Faraday coined the use of "nucleus" for the dense centre of an atom, a theoretical idea at the time, long before anyone could observe such a thing. The biological sense of the central housing of a cell's chromosomes followed the same pattern of borrowing a classical term for a central, core part.

Synonyms: core, center, hub

Antonyms: periphery, outer layer