Definition of nucleus in US English:



  • 1The central and most important part of an object, movement, or group, forming the basis for its activity and growth.

    ‘the nucleus of a film-producing industry’
    • ‘Christine Maggiore is the outspoken nucleus of a movement to help HIV-positive mothers who question medication.’
    • ‘The nucleus of the future Impressionist movement was born.’
    • ‘Fairs form the nucleus for frenetic autumn activity in London and New York, while a princely collection is auctioned at a fairy-tale castle in Germany’
    • ‘It was a medieval library serving as the nucleus of a range of activities in the fields of art, religion, history and literature.’
    • ‘These embryonic communities created an important nucleus for post-war migration, which was fuelled by economic factors.’
    • ‘By the end of the 1850s a nucleus of business houses had been established.’
    • ‘If this proposal is accepted, the government together with the St Lucian organizations could have an extension of the mission in Brooklyn and an important nucleus for the St Lucian community.’
    • ‘Without the ‘woman’, there will be a crippling lacuna, since it is her nurturing instinct that anchors the family making her a nucleus around which every member rallies.’
    • ‘It was happy to see the destruction of the Polish resistance movement, which had formed the nucleus of the support for the Polish government-in-exile.’
    • ‘In addition to being the center of religious training and worship, the church served as the nucleus of social activities and a conduit for the dispersion of social services.’
    • ‘As already stated, the placing of bets and payment of winnings form the nucleus of the gambling activity.’
    • ‘The Manchester centre is the nucleus of a hi-tech surveillance system and features an 18-metre monitor wall that can display up to 180 high-resolution images.’
    • ‘Senate House and a nucleus of colleges were built in Bloomsbury in the late 1930s.’
    • ‘At school, Qaddafi participated in a small group of politically active friends - a group which was eventually to form the nucleus of the Free Officers Movement.’
    • ‘In the middle of these green acres, a modest cluster of white greenhouses make up the nucleus of daily activity.’
    • ‘His own drawings form the nucleus of an important collection of architectural drawings.’
    • ‘He built the famous Stone House at Ooty that formed the nucleus of Government offices and is now part of the Government Arts College.’
    • ‘And at the moment there is not even the nucleus of a movement to achieve that.’
    • ‘The nucleus of the global movement against injustice will not - cannot, should not - be found in the centers of global privilege.’
    • ‘In 1911, the first dairy cows and other livestock arrived to become the nucleus of USDA's animal husbandry research activities.’
    core, centre, central part, most important part, heart, nub, hub, middle, midpoint, eye, kernel, focus, focal point, pivot, crux
    View synonyms
    1. 1.1Physics The positively charged central core of an atom, consisting of protons and neutrons and containing nearly all its mass.
      • ‘Every atomic nucleus consists of a certain number of protons, strongly bound to a certain number of neutrons.’
      • ‘Electrons produce a small magnetic field as they spin and orbit the nucleus of an atom.’
      • ‘Most atomic nuclei consist of clusters of protons and neutrons (which have no electrical charge).’
      • ‘Electrons are found in clouds that surround the nucleus of an atom.’
      • ‘The harmless radio waves excite protons that form the nuclei of hydrogen atoms in the body.’
    2. 1.2Biology A dense organelle present in most eukaryotic cells, typically a single rounded structure bounded by a double membrane, containing the genetic material.
      • ‘Dense granules surrounding the nucleus are probably cytoplasmic organelles.’
      • ‘The cells were characterized by large vesicular nuclei with single large nucleoli.’
      • ‘The cells had round or oval vesicular nuclei with multiple prominent nucleoli.’
      • ‘Further, interphase nuclei appeared disintegrated and some mitotic figures were clumped together.’
      • ‘The cells possessed eosinophilic cytoplasm, well-defined cell borders, and vesicular nuclei with small, conspicuous nucleoli.’
    3. 1.3Anatomy A discrete mass of gray matter in the central nervous system.
      • ‘The pontocerebellar fibers connect pontine nuclei with the cerebellar cortex of the opposite side, via the middle cerebellar peduncles.’
      • ‘The trochlear nerve nuclei are located ventral to the mesencephalic aqueduct.’
      • ‘The term extrapyramidal system refers to the basal ganglia and several brain stem nuclei with which they are connected.’
      • ‘These effects are produced by fibres projecting from the hypothalamus to parasympathetic nuclei in the brain stem, and to sympathetic centres in the spinal cord.’
      • ‘Axons travel from the neurons located in nuclei within the brain stem via the cranial nerves without synaptic interruption to the motor end plates on the striated muscle.’
    4. 1.4Astronomy The solid part of the head of a comet.
      • ‘The spacecraft will orbit the comet's nucleus.’
      • ‘Sometimes, the stresses are strong enough to break off chunks of the comet's nucleus.’
      • ‘Another difficulty that must be resolved is the current uncertainty about the consistency of cometary nuclei.’
      • ‘The spacecraft's point of view now captures the shadowed side of the comet's nucleus.’
      • ‘Indeed, the outermost asteroids show similarities with the cometary nuclei observed far from the Sun.’


Early 18th century: from Latin, literally ‘kernel, inner part’, diminutive of nux, nuc- ‘nut’.