English Reference
noun · verb

fission

n. · v.
US /ˈfɪʃən/ UK /fˈɪʃən/ fis·sion UK spelling fissioned, fissions

  1. 01 C1 Advanced Technical Science

    n.the splitting of an atom's center to release a large amount of energy.

    n.the process in which the nucleus of a heavy atom splits into two or more smaller nuclei, releasing significant energy.

    Simple

    Nuclear power plants use fission to create the heat needed for electricity.

    In context

    The discovery of nuclear fission in the late 1930s fundamentally altered the landscape of both global energy production and modern warfare.

    Usage

    Often used as a modifier in the phrase 'nuclear fission'.

    splittingnuclear decay
  2. 02 C2 Proficiency Technical Science

    n.a way that some tiny living things, like bacteria, reproduce by splitting in two.

    n.a form of asexual reproduction in single-celled organisms where the parent cell divides into two or more daughter cells.

    Simple

    Bacteria reproduce quickly through a process called binary fission.

    In context

    During binary fission, the genetic material is replicated before the cell membrane pinches inward to create two genetically identical organisms.

    Usage

    Commonly appears in the specific biological term 'binary fission'.

    divisionbinary fission
  3. 03 C2 Proficiency Technical Science

    v.to split into two or more parts, or to cause something to split.

    v.to undergo or cause to undergo the process of splitting into parts.

    Simple

    The heavy atoms began to fission when they were hit by neutrons.

    In context

    Under specific laboratory conditions, the researchers observed the isotopes as they began to fission at an accelerated rate.

    Usage

    Used both transitively and intransitively in scientific contexts.

Generating electricity from the heat unleashed by fissioning uranium atoms is a multistep process, and at each step the composition of the nuclear fuel must be reassessed before proceeding.

Phys.org· 10 Sept 2026

Long-lived radioactive fission products keep decaying for months or even years, releasing a weak stream of particles called antineutrinos.

ScienceDaily· 14 Aug 2026

Borrowed from Latin fissiōnem, accusative singular of fissiō (“the act of breaking up”), from findō (“split, divide”).

Etymology adapted from Wiktionary, available under CC BY-SA 4.0.

This entry
Origin Latin fissiōnem
Level C2 · Proficiency
Frequency Occasional
Updated