- Positively-charged particle with mass almost identical to that of the neutron, and found with neutrons in the nuclei of atoms
(written as Proton)Russian (and former Soviet) rocket launcher used extensively in manned and unmanned spaceflight The name was also used in the 1960s for a series of Soviet satellites used to investigate cosmic rays
- A positively charged extremely stable subatomic particle which is present in all atomic nuclei. Its mass is about 1,840 times that of an electron, and slightly less than that of a neutron. A protium nucleus consists of a single proton. It is the lightest baryon, and its antiparticle is the antiproton. The number of protons in a nucleus is what differentiates all chemical elements. Protons are used, for instance, in particle accelerators.