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positronium

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noun pos·i·tro·ni·um \ ˌpä-zə-ˈtrō-nē-əm \

Definition of positronium

:a short-lived system that consists of a positron and an electron bound together and is suggestive of a hydrogen atom

First Known Use of positronium

1945

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Britannica.com: Encyclopedia article about positronium

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