fission

[ fish-uhn ]

noun

1. the act of cleaving or splitting into parts.
2. Also called nu·cle·ar fis·sion [noo, -klee-er , fish, -, uh, n, nyoo, -]. Physics. the splitting of the nucleus of an atom into nuclei of lighter atoms, accompanied by the release of energy. Compare fusion ( def 4 ).
3. Biology. the division of an organism into new organisms as a process of reproduction.

verb (used without object)

1. Physics. to undergo fission.

verb (used with object)

1. Physics. to cause to undergo fission.

fission

/ ˈfɪʃən /

noun

1. the act or process of splitting or breaking into parts
2. biology a form of asexual reproduction in single-celled animals and plants involving a division into two or more equal parts that develop into new cells
3. See nuclear fission
   short for nuclear fission

fission

/ fĭsh′ən /

1. The splitting of an unstable atomic nucleus into two or more nuclei. Fission occurs spontaneously, generally when a nucleus has an excess of neutrons, resulting in the inability of the strong force to bind the protons and neutrons together. The fission reaction used in many nuclear reactors and bombs involves the absorption of neutrons by uranium-235 nuclei, which immediately undergo fission, releasing energy and fast neutrons .
2. Compare fusion
3. A process of asexual reproduction in which a single cell splits to form two identical, independent cells. In fission, the chromosomal DNA replicates before the cell divides. Most bacteria and other prokaryotes reproduce by means of fission.
4. Also called binary fission

Word History and Origins

Origin of fission¹

First recorded in 1835–45; from Latin fissiōn- (stem of fissiō ) “a splitting, dividing,” equivalent to fiss(us) “divided” + -iōn- noun-forming suffix; fissi-, -ion; fission def 2 was first recorded in 1935–40

Word History and Origins

Origin of fission¹

C19: from Latin fissiō a cleaving

Example Sentences

Each fission also releases additional neutrons, which bounce around within the reactor at a variety of energies.

From Science News

Meitner was nominated for the prize — sometimes in physics, other times in chemistry — a whopping 48 times, most after the discovery of fission.

From Science News

Hahn received the 1944 Nobel Prize in chemistry for the discovery of fission, but Meitner never won a Nobel, in a decision now widely considered unjust.

From Science News

So we have to have other paths—like fission or fusion—that can give us that reliable source of electricity, which we’ll be even more dependent on than ever.

From MIT Technology Review

Seaborg recalled that at first Oppenheimer didn’t believe fission happened.

From Science News

One of the isotopes of fission products, when fuel melts, is an iodine isotope, and it goes in your body through your thyroid.

From The Daily Beast

Rick turned in time to see the side of El Viejo blow off in an explosion that made ten kilotons of fission seem puny indeed.

From Project Gutenberg

The United States, indeed, is still in the process of fusion following the earlier fission process.

From Project Gutenberg

Some bacilli after fission retain a characteristic arrangement and may be spoken of as Diplobacilli or Streptobacilli.

From Project Gutenberg

Such broad groupings as these have, however, but little practical value when applied to the systematic study of the fission fungi.

From Project Gutenberg

Prior to maturity the future line of fission is plainly indicated by the difference in color.

From Project Gutenberg