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

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

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

This does not mean life has been confirmed on Mars.

From Science Daily • Feb. 12, 2026

“That is hugely significant, because if that happens twice in our solar system, it could mean life is really common,” he says.

From BBC • Oct. 13, 2024

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

From Seattle Times • May 19, 2024

Still, Nye was glad to have seen it; each item—the palliatives for sore gums, the greasy Honolulu pillow—gave him a clearer impression of the owner and his lonely, mean life.

From "In Cold Blood" by Truman Capote

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