Definition of fission in English:



  • 1[mass noun] Division or splitting into two or more parts.

    ‘the party dissolved into fission and acrimony’
    • ‘Because tribes are so segmental and undifferentiated, their constituent parts - e.g., families, lineages, clans - tend to oscillate between fusion and fission.’
    • ‘In either case, she is no longer with him, another fission in this song of mournful departures.’
    • ‘We hope that further experimental studies will reveal fission and fusion promotion processes in real systems.’
    • ‘This has exposed deep fissions within the legal fraternity.’
    • ‘This process of fission may then spread beyond the borders of the state itself, as refugee populations flee across the border, and as insurgent groups use frontier zones for their base camps.’
    • ‘However, conflicts among households of the same lineage would periodically erupt and often lead to further fissions within the lineage.’
    • ‘As already noted in the context of the collapse of communism, this challenge to the map has taken the form both of fission and fusion.’
    • ‘The bigger religions all experienced fissions serious enough to redivide the larger communities that they created.’
    • ‘The history of human beings is not one of separate and permanent cultures, but one of continual migration, amalgamation, fission and disintegration.’
    • ‘During fission, a nucleus splits into two nuclei of less mass with greater stability.’
    • ‘There are many great ideas for both fission and fusion.’
    • ‘Several of these new departments have been reorganised on a number of occasions to accommodate shifting trends in policy, through what might be referred to as a process of fission and fusion.’
    • ‘The ecclesiastical fission has led to some tiny island villages being split religiously among as many as five different bodies.’
    • ‘These internal fissions, he surmised, explained the low voter turnout in traditionally Republican areas of the state.’
    • ‘In the current wave, processes of fission and disintegration predominate.’
    • ‘The fission process itself provides a mechanism for creating a so-called ‘chain reaction.’’
    • ‘They also suggest that the area's history of fusion and fission present a microcosm of the ethnic and political tensions of the Nigerian nation since independence.’
    splitting, parting, division, dividing, cleaving, rupture, breaking, severance, separation, disjuncture
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    1. 1.1Biology Reproduction by means of a cell or organism dividing into two or more new cells or organisms.
      ‘bacteria divide by transverse binary fission’
      • ‘We considered a model in which the proliferating cells divide by binary fission.’
      • ‘Amoebas are single-celled water creatures that multiply by fission: an amoeba will split down the middle to become two amoebas.’
      • ‘Bacteria divide symmetrically during normal growth and have a central constriction to bring about binary fission of the cell.’
      • ‘Primarily they reproduce asexually, which they accomplish by binary fission, or simple cell division.’
      • ‘Apparently, this creature reproduces by binary fission, a process common to the single cell creatures of earth.’
    2. 1.2
      ‘the fission of uranium atoms in a chain reaction’
      short for nuclear fission
      [as modifier] ‘a fission product’
      • ‘Because fission releases additional neutrons, a chain reaction can take place.’
      • ‘In most cases, the purpose of a nuclear reactor is to capture the energy released from fission reactions and put it to some useful service.’
      • ‘It produces no fission radioactive by-products or fallout of serious concern.’
      • ‘Uranium fission plants in the US are presently supplying less than 8% of our total energy demand.’
      • ‘These fission products are not found in natural background radiation, but are exclusively byproducts of nuclear weapons explosions and nuclear reactor operations.’
      splitting, parting, division, dividing, cleaving, rupture, breaking, severance, separation, disjuncture
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  • (chiefly of atoms) undergo fission.

    ‘these heavy nuclei can also fission’
    • ‘One of the differences between U235 and its common relative U238 is that U235 fissions very easily.’
    • ‘Of this, it is estimated that only about 2% actually fissioned.’
    • ‘Most of the transuranium elements have isotopes that disintegrate by fissioning in addition to emitting alpha particles.’
    • ‘We will assume that once a seed has fissioned once, it continues to fission or effectively double in a time t 2, which is independent of the above distribution.’
    • ‘Uranium 235 is the isotope that fissions, but it is an extremely small part of natural uranium; only 7 atoms in 1, 000.’


Early 17th century: from Latin fissio(n-), from findere to split.