Latin for Writers V

This week on Gather I read an article which I found interesting and well-written, except for one flaw: the writer had used the word criteria as a single noun. This is an easy mistake to make, because in English a noun ending in "a" is most likely to be single. We look for an "s" when we deal with plurals. However, English has borrowed numerous nouns directly from Latin. In Latin, if a noun is neuter, its plural is likely to end in "a." Here are some examples: criteria, phenomena, data, strata, media, addenda, memoranda. All these words are plural in both Latin and English. Their singular forms in Latin would be criterion, phenomenon, datum, stratum, medium, addendum, and memorandum.

In Latin, agendum means something that needs to be done; when more than one thing needs to be done, the word is agenda. When we make up a list of things to do and call it an agenda, we are using a Latin plural as an English singular word. As a collective noun (actually, it's a verb form used as a noun) it may be used as a singular or a plural word.
In English the word data is also established as a singular and a plural noun.