duodecennial

adjective

du·​o·​decennial

¦d(y)ü(ˌ)ō+

: occurring once in 12 years

Word History

Etymology

Late Latin duodecennium period of 12 years (from Latin duodecim twelve—from duo two + -decim, from decem ten—+ -ennium, from annus year) + English -al

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