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.

Dr. Yasuyuki Nagashima is a Professor in the Department of Physics at Tokyo University of Science, Japan, specializing in positron and positronium physics.

From Science Daily • Apr. 28, 2026

Because positronium carries no electric charge, it may be useful for analyzing material surfaces without causing damage.

From Science Daily • Apr. 28, 2026

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

From Science Daily • Apr. 28, 2026

As the positronium atoms passed through the two-to-three-layer graphene sheet, some of them made it through and were detected.

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