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Topic: Units of Time
also read: Original Letter \| Reply Letter #1

Dear Editor,
Paul R. Renne and Igor M. Villa in the October issue and Andrew V. Okulitch in the April/May issue discuss the use of annum (a) and its multiples ka, Ma, Ga. The former don't use any plural form in their text, the latter uses "anna".

Whether they are intervals or points in time, there appears to be a consensus that Ma stands for "mega-annum" with a plural "mega-annums", and correspondingly for a, ka and Ga. I presume what is involved is the Latin for "year". This is "annus" in the nominative singular, the standard form for citation. Why "annum", the accusative singular is used, I don't know (perhaps greater familiarity from phrases such as "per annum"), but it is.

"Anna" in Latin is only a feminine personal name and there is no excuse for using it to mean years.

Daniel J. Milton
Vienna VA

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