positronium

American

[poz-i-troh-nee-uhm] / ˌpɒz ɪˈtroʊ ni əm /

noun

Physics.

a short-lived atomic system consisting of a positron and an electron bound together.

positronium British

/ ˌpɒzɪˈtrəʊnɪəm /

noun

physics a short-lived entity consisting of a positron and an electron bound together. It decays by annihilation to produce two or three photons

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Etymology

Origin of positronium

First recorded in 1945; positron + -ium; coined by Arthur E. Ruark (1899–1979), U.S. physicist

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

His research focuses on the properties of negative ions of positronium and the positronium beam.

From Science Daily • Apr. 28, 2026

Compared with earlier techniques, this method produces positronium beams with higher energies, reaching up to 3.3 keV.

From Science Daily • Apr. 28, 2026

Dr. Yugo Nagata is an Associate Professor in the Department of Physics at Tokyo University of Science, Japan, specializing in positronium and atomic physics.

From Science Daily • Apr. 28, 2026

However, despite these advances, this phenomenon had not been directly observed in positronium.

From Science Daily • Apr. 28, 2026

Up until now the coldest temperatures for positronium in a vacuum has been around 100C.

From BBC • Feb. 22, 2024

Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023