mean life

American

noun

Physics.

the average time that an unstable particle or nucleus survives before it decays.
decay time.

mean life British

noun

τ. physics the average time of existence of an unstable or reactive entity, such as a nucleus, elementary particle, charge carrier, etc; lifetime. It is equal to the half-life divided by 0.693 15

"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

Example Sentences

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mean life

One example is extensive, independent testing to ensure the effectiveness and reliability of critical systems, which can mean life or death for servicemembers.

From The Wall Street Journal ● Apr. 16, 2026

Ms Ming said that "life should mean life".

From BBC ● Oct. 6, 2025

“It could mean life or death,” McDuffie said.

From Seattle Times ● May 19, 2024

Because pinpointing a food allergy could mean life or death, an accurate diagnosis is critical.

From Science Daily ● Nov. 7, 2023

It was too hard to know which action to take when the choices might mean life or death.

From "Earthquake Terror" by Peg Kehret

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