carbon 12

noun (1)

Definition of carbon 12

 (Entry 1 of 4)

: an isotope of carbon of mass number 12 that is the most abundant carbon isotope and is used as a standard for measurements of atomic weight

12-step

adjective
\ ˈtwelv-ˌstep How to pronounce 12-step (audio) \

Definition of 12-step (Entry 2 of 4)

: of, relating to, characteristic of, or being a program that is designed especially to help an individual overcome an addiction, compulsion, serious shortcoming, or traumatic experience by adherence to 12 tenets emphasizing personal growth and dependence on a higher spiritual being

12 a.m.

noun (2)

Definition of 12 a.m. (Entry 3 of 4)

: midnight : one hour after 11 p.m.

12 p.m.

noun (3)

Definition of 12 p.m. (Entry 4 of 4)

: one hour after 11 a.m. : noon

First Known Use of carbon 12

Noun (1)

1936, in the meaning defined above

Adjective

1983, in the meaning defined above

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The first known use of carbon 12 was in 1936

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