proton

American  

[proh-ton] / ˈproʊ tɒn /

noun

Physics, Chemistry.

• protons
  plural

1. a positively charged elementary particle that is a fundamental constituent of all atomic nuclei. It is the lightest and most stable baryon, having a charge equal in magnitude to that of the electron, a spin of ½, and a mass of 1.673 × 10 -27 kg. P

---

proton British  

/ ˈprəʊtɒn /

noun

1. a stable, positively charged elementary particle, found in atomic nuclei in numbers equal to the atomic number of the element. It is a baryon with a charge of 1.602176462 × 10 ^–19 coulomb, a rest mass of 1.672 62159 × 10 ^–27 kilogram, and spin 1/ 2

---

proton Scientific  

/ prō′tŏn′ /

1. A stable subatomic particle in the baryon family having a mass of 1.672 × 10 ^{- 24} grams (1,836 times that of the electron) and a positive electric charge of approximately 1.602 × 10 ^{- 19} coulombs. Protons make up part of the nucleus of all atoms except hydrogen, whose nucleus consists of a single proton. In neutral atoms, the number of protons is the same as the number of electrons. In positively charged atoms, the number of protons is greater than the number of electrons, and in negatively charged atoms electrons outnumber protons. Protons are believed to be composed of two up quarks and one down quark.

2. See Table at subatomic particle

---

proton Cultural  

1. An elementary particle with a positive charge, found in the nucleus of an atom.

---

Discover More

Protons and neutrons make up most of an atom's mass.

A proton is over a thousand times heavier than an electron.

Other Word Forms

Derived Forms

• protonic
  adjective

Inflected Forms

Nouns

• protons
  plural

Etymology

Origin of proton

Term first suggested in 1920 by English physicist Ernest Rutherford as noun use of Greek prôton, neuter of prôtos “first,” the proton being the constituent of hydrogen nuclei, and formed on the analogy of electron; see first, electron

Compare meaning

How does proton compare to similar and commonly confused words? Explore the most common comparisons:

• proton vs. electron

Explanation

Atoms are made up of three main particles: protons, electrons, and neutrons. A proton has a positive electrical charge, while electrons are negative. The number of protons and electrons is equal in each atom. The atomic number of an element, which is the number in the upper left corner of its box on the periodic table, is the number of protons in each atom. The hydrogen atom, for example, has just one proton, so it also has one electron and its atomic number is 1. If you have an atom with two protons in its nucleus, you know it can't be a hydrogen atom.

Example Sentences

See Examples For:

proton protons

Antidepressants, beta-blockers, proton pump inhibitors, and benzodiazepines were also associated with distinctive microbial "fingerprints."

From Science Daily ● Aug. 24, 2026

"But at high energy, gluons within the proton split and multiply."

From Science Daily ● Aug. 16, 2026

Understanding why requires looking at the changing internal structure of a proton as its energy increases.

From Science Daily ● Aug. 16, 2026

"In the naïve quark model, there are three quarks inside a proton, but nothing else," said Tommy Tsang, formerly a postdoc at Kent State University, now at DOE's Argonne National Laboratory.

From Science Daily ● Aug. 16, 2026

But it bristled with Lawrence’s self-confidence and his manner of intuitively grasping possibilities well ahead of realities—in this case, the production of sustained resonant proton beams with a million volts of kinetic energy.

From "Big Science" by Michael Hiltzik

In this process, a photon beam strikes protons held inside a fixed target.

From Science Daily ● Sep. 2, 2026

They then bombarded the gas mixture with protons to imitate the stream of energetic particles generated by solar superflares.

From Science Daily ● Sep. 2, 2026

It helps explain the extraordinary stability of protons, which form a central part of atomic nuclei and do not appear to decay under ordinary circumstances.

From Science Daily ● Aug. 16, 2026

"The open channel structure also helps the ion-containing material, such as an ionomer, spread evenly and makes it easier for protons, oxygen and water to move through the electrode," Wu continued.

From Science Daily ● Aug. 8, 2026

By then all the stars will have burned out and the protons and neutrons in them will probably have decayed into light particles and radiation.

From "A Brief History of Time: And Other Essays" by Stephen Hawking