Proton Definition

prōtŏn

protons

noun

A nucleon carrying a positive charge equal to the negative charge of an electron and having a mass of c. 1.673 × 10^-27 kg (c. 938.2796 MeV/c², c. 1,836 times the mass of an electron): the number of protons in an atom determines the atomic number of a chemical element.

Webster's New World

(physics) Positively charged subatomic particle forming part of the nucleus of an atom and determining the atomic number of an element; the nucleus of the most common isotope of hydrogen; composed of two up quarks and a down quark.

Wiktionary

Other Word Forms of Proton

Noun

Singular:

proton

Plural:

protons

Origin of Proton

From Greek prōton neuter of prōtos first per¹ in Indo-European roots

From American Heritage Dictionary of the English Language, 5th Edition
From Ancient Greek πρῶτον (prōton), neuter of πρῶτος (prōtos, “first")

From Wiktionary