What does nucleus mean?
A nucleus is a central structure or organizing part. In living cells, it is the membrane-bound control center that contains chromosomes and helps regulate cell activities. In physics, the nuclear term refers to the dense, positively charged center of an atom, where protons and neutrons are found. In broader usage, a nucleus means the fundamental center around which something is organized, such as the core idea or administrative heart of an organization. The word is usually formal and technical, although its metaphorical sense is widely understood. It is especially associated with biology and nuclear science, where precise distinctions matter: the cell nucleus, the atomic nucleus, and related structures such as the nucleolus are different things. The standard plural is nuclei, with the singular pronunciation stressed on the first syllable.
The central, typically rounded part of a biological cell, containing chromosomes and other material involved in controlling cellular activity.
"The nucleus directs the cell's growth, metabolism, and reproduction."
Usually refers to the nucleus of a eukaryotic cell; prokaryotic cells do not have a membrane-bound nucleus.
The positively charged central region of an atom, containing protons and neutrons.
"The atomic nucleus contains nearly all of an atom's mass."
A technical term in physics and chemistry, usually used with terms such as atomic, nuclear, and proton.
A central, fundamental, or defining part of a larger structure, organization, or body of ideas.
"The proposal formed the nucleus of the committee's recommendations."
This is a formal metaphorical use and is common in political, organizational, and analytical writing.
The standard plural is nuclei. It is commonly pronounced with the first syllable stressed.
"The cell contains several nuclei after division."
Every living cell has a control center, but the word nucleus literally comes from the Latin word for a small nut: the part at the heart of the cell.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does nucleus come from?
The word comes from Latin nucleus, a diminutive of nux, meaning “nut.” Latin used the word for the kernel inside a nut, and it was later applied to the central parts of atoms and cells. English borrowed the term in the 17th century, initially in anatomical and scientific contexts. Its scientific meanings developed alongside the study of cells and atomic structure, while its figurative use for a central core became common later.
Related word forms
How nucleus is actually used
In biology and physics, the term is technical and normally refers to a specific structure. In general use, it is formal and means the central or essential part of something. The usual plural is nuclei.
Easily confused with nucleus
A nucleolus is a structure inside the cell nucleus, whereas a nucleus is the larger organelle that contains the cell's genetic material.