nucleus
- 01 B2 Upper Intermediate
the central part of a living cell that contains its genetic information and controls its growth.
a membrane-bound organelle within eukaryotic cells containing the genetic material and governing cellular activity.
Simple“The biology teacher showed us how the nucleus holds the DNA of the cell.”
In context“Under the microscope, the nucleus appeared as a dense, dark-stained sphere, clearly separated from the surrounding cytoplasm by its own membrane.”
UsageThe plural form is 'nuclei'.
- 02 B2 Upper Intermediate
the small, heavy center of an atom that contains protons and neutrons.
the positively charged central core of an atom, consisting of protons and neutrons and containing nearly all its mass.
Simple“Energy is released when the nucleus of a heavy atom is split.”
In context“The stability of an isotope depends largely on the ratio of neutrons to protons within its nucleus.”
UsageThe plural form is 'nuclei'.
Synonymsatomic core - 03 C1 Advanced
the small, central group of people or things that a larger group grows around.
the central or essential part around which other parts are gathered or a group is formed.
Simple“A small nucleus of dedicated volunteers started the charity ten years ago.”
In context“The original research team formed the nucleus of the new department, providing the expertise necessary to attract further funding.”
Teacher's tipIn this figurative sense, it describes the 'seed' or 'starting point' of a larger organization.
- 04 C2 Proficiency
the central part of a syllable, which is usually a vowel sound.
the central part of a syllable, typically consisting of a vowel or a syllabic consonant.
Simple“In the word 'cat', the vowel 'a' is the nucleus of the syllable.”
In context“Phonologists distinguish between the onset of a syllable and its rhyme, the latter of which is composed of the nucleus and an optional coda.”
Synonyms
“It makes messages, copying and carrying instructions from the cell nucleus to make proteins.”
“Instead of studying zinc-70 directly, they examined the beta decay of two separate states of its parent nucleus, copper-70.”
Learned borrowing from Latin nucleus (“kernel, core”). The earliest uses refer to the head of a comet and the kernel of a seed, both recorded in Lexicon Technicum in 1704. The sense in atomic physics was coined by British scientist Michael Faraday in 1844 in a theoretical meaning.
Etymology adapted from Wiktionary, available under CC BY-SA 4.0.