Herewith an erratum on data
And a datum on errata,
And errata on datum,
And data on erratum:

A fact or principle denied by none is a datum.
Go down a list of errors and pick one; it’s an erratum.
Add a datum to a datum;
You have data.
Add erratum to erratum;
You have errata.

Erratum is, and datum is;
Errata are, and data are;
Except that errata is the plural of erratum,
And data is the plural of datum.

But otherwise,
Gals and guys,
Gee whiz—
Don’t say errata is.
I also bar
Saying datum are.

—Willard R. Espy, as seen in the July, 1985, issue of Writer's Digest.