15 Subatomic Word Origins

In July 2017, researchers at the European Organization for Nuclear Research (CERN) found evidence for a new fundamental particle of the universe: Ξcc++, a special kind of Xi baryon that may help scientists better understand how quarks are held together. Is that Greek to you? Well, it should be. The names for many of the particles that make up the universe—as well as a few that are still purely theoretical—come from ancient Greek. Here’s a look at 15 subatomic etymologies.

1. ION

An ion is any atom or molecule with an overall electric charge. English polymath William Whewell suggested the name in an 1834 letter to Michael Faraday, who made major discoveries in electromagnetism. Whewell based ion on the ancient Greek verb for “go” (ienai), as ions move towards opposite charges. Faraday and Whewell had previously considered zetode and stechion.

2. ELECTRON

George Stoney, an Anglo-Irish physicist, introduced the term electron in 1891 as a word for the fundamental unit of charge carried by an ion. It was later applied to the negative, nucleus-orbiting particle discovered by J. J. Thomson in 1897. Electron nabs the -on from ion, kicking off the convention of using -on as an ending for all particles, and fuses it with electric. Electric, in turn, comes from the Greek for “amber,” in which the property was first observed. Earlier in the 19th century, electron was the name for an alloy of gold and silver.

3. PROTON

The electron’s counterpart, the positively charged proton in the nuclei of all atoms, was named by its discoverer, Ernest Rutherford. He suggested either prouton or proton in honor of William Prout, a 19th-century chemist. Prout speculated that hydrogen was a part of all other elements and called its atom protyle, a Greek coinage joining protos ("first") and hule ("timber" or "material") [PDF]. Though the word had been previously used in biology and astronomy, the scientific community went with proton.

4. NEUTRON

Joining the proton in the nucleus is the neutron, which is neither positive nor negative: It’s neutral, from the Latin neuter, “neither.” Rutherford used neutron in 1921 when he hypothesized the particle, which James Chadwick didn’t confirm until 1932. American chemist William Harkins independently used neutron in 1921 for a hydrogen atom and a proton-electron pair. Harkins’s latter application calls up the oldest instance of neutron, William Sutherland’s 1899 name for a hypothetical combination of a hydrogen nucleus and an electron.

5. QUARK

Protons and neutrons are composed of yet tinier particles called quarks. For their distinctive name, American physicist Murray Gell-Mann was inspired in 1963 by a line from James Joyce’s Finnegan’s Wake: “Three quarks for Muster Mark.” Originally, Gell-Mann thought there were three types of quarks. We now know, though, there are six, which go by names that are just as colorful: up, down, charm, strange, top, and bottom.

6. MESON

Made up of a quark and an antiquark, which has identical mass but opposite charge, the meson is a short-lived particle whose mass is between that of a proton and an electron. Due to this intermediate size, the meson is named for the ancient Greek mesos, “middle.” Indian physicist Homi Bhabha suggested meson in 1939 instead of its original name, mesotron: “It is felt that the ‘tr’ in this word is redundant, since it does not belong to the Greek root ‘meso’ for middle; the ‘tr’ in neutron and electron belong, of course, to the roots ‘neutr’ and ‘electra’.”

7., 8., AND 9. BOSON, PHOTON, AND GLUON

Mesons are a kind of boson, named by English physicist Paul Dirac in 1947 for another Indian physicist, Satyendra Nath Bose, who first theorized them. Bosons demonstrate a particular type of spin, or intrinsic angular momentum, and carry fundamental forces. The photon (1926, from the ancient Greek for “light”) carries the electromagnetic force, for instance, while the gluon carries the so-called strong force. The strong force holds quarks together, acting like a glue, hence gluon.

10. HADRON

In 2012, CERN’s Large Hadron Collider (LHC) discovered a very important kind of boson: the Higgs boson, which generates mass. The hadrons the LHC smashes together at super-high speeds refer to a class of particles, including mesons, that are held together by the strong force. Russian physicist Lev Okun alluded to this strength by naming the particles after the ancient Greek hadros, “large” or “bulky,” in 1962.

11. LEPTON

Hadrons are opposite, in both makeup and etymology, to leptons. These have extremely tiny masses and don’t interact via the strong force, hence their root in the ancient Greek leptos, “small” or “slender.” The name was first suggested by the Danish chemist Christian Møller and Dutch-American physicist Abraham Pais in the late 1940s. Electrons are classified as leptons.

12. BARYON

Another subtype of hadron is the baryon, which also bears the stamp of Abraham Pais. Baryons, which include the more familiar protons and neutrons, are far more massive, relatively speaking, than the likes of leptons. On account of their mass, Pais put forth the name baryon in 1953, based on the ancient Greek barys, “heavy” [PDF].

13. AXION

Quirky Murray Gell-Mann isn't the only brain with a sense of humor. In his 2004 Nobel Prize lecture, American physicist Frank Wilczek said he named a “very light, very weakly interacting” hypothetical particle the axion back in 1978 “after a laundry detergent [brand], since they clean up a problem with an axial current” [PDF].

14. TACHYON

In ancient Greek, takhys meant “swift,” a fitting name for the tachyon, which American physicist Gerald Feinberg concocted in 1967 for a hypothetical particle that can travel faster than the speed of light. Not so fast, though, say most physicists, as the tachyon would break the fundamental laws of physics as we know them.

15. CHAMELEON

In 2003, the American physicist Justin Khoury and South African-American theoretical physicist Amanda Weltman hypothesized that the elusive dark energy may come in the form of a particle, which they cleverly called the chameleon. Just as chameleons can change color to suit their surroundings, so the physical characteristics of the chameleon particle change “depending on its environment,” explains Symmetry, the online magazine dedicated to particle physics. Chameleon itself derives from the ancient Greek khamaileon, literally “on-the-ground lion.”

For more particle names, see Symmetry’s “A Brief Etymology of Particle Physics,” which helped provide some of the information in this list.