pion

[ pahy-on ]

noun

, Physics.

1. the first meson to be discovered: it has spin 0 and may be positively or negatively charged or neutral; charged pions decay into a muon and a neutrino or antineutrino. : π

pion

/ ˈpaɪɒn /

noun

1. physics a meson having a positive or negative charge and a rest mass 273.13 times that of the electron, or no charge and a rest mass 264.14 times that of the electron

pion

/ pī′ŏn′ /

1. A meson occurring either in a neutral form with a mass 264 times that of an electron and a mean lifetime of 8.4 × 10 ^-17 seconds or in a positively or negatively charged form with a mass 273 times that of an electron and a mean lifetime of 2.6 × 10 ^-8 seconds. The pion was once believed to be the particle that mediates the strong force , which holds nucleons together in the nucleus; it is now believed that the gluon is the mediator particle. Pions do interact with nucleons, however, and are able to transform neutrons into protons and vice versa.
2. Also called pi-meson
3. See Table at subatomic particle

Word History and Origins

Origin of pion¹

First recorded in 1950–55; pi (meson) + -on ¹

Word History and Origins

Origin of pion¹

C20: from Greek letter pi ¹+ on

Example Sentences

Specifically, the proton morphs into a neutron and a pion made of one up quark and one down antiquark.

From Quanta Magazine

The pion saplings, which the dancers also pretended to swallow, had no deceptive arrangement.

From Project Gutenberg

In reality, each boy is an unpaid pion, a watchdog whose vigilance never relaxes.

From Project Gutenberg

Pion; A certaine great, round, and Bulbus-rooted flower, of one whole colour.

From Project Gutenberg

Close at hand was a pion tree, which spread out low-growing branches all about.

From Project Gutenberg

Both the pion and the camass are largely utilized even at the present day for food by the Indians.

From Project Gutenberg