Well, I'm not done with plurals of Latin words yet, but I promise I'll talk about a different usage issue next week.
Back in my dictionary-writing days, one of our eager correspondents inquired why no plural form is given for the word "status" in The Canadian Oxford Dictionary. Merriam-Webster's Collegiate Dictionary, Tenth Edition, he went on, gives the plural as "statuses" which, he said, "sounds ridiculous and would make it the only Latin derivative with an "es" ending. As far as I am concerned I consider the plural to be "stati" and I would like to know why this is not in the dictionary."
The word "status" is not given a plural because it is a regular noun (forming the plural in -s or -es if ending in a sibilant). This is something that English native speakers can intuitively do.
"Status" has been in the English language since the late 17th century. It has been consistently printed in roman rather than italic type, indicating that it is fully naturalized, since the mid-19th century. Fully naturalized words in English usually form their plurals according to English rules rather than according to the rules of the language from which they were borrowed (otherwise we would talk about the "stamina" of a flower rather than its stamens). The OED entry for the word, which would have been edited in about 1910-15, gave the plural "(rare) status", pronounced "stay tee us", since the plural in Latin is, surprisingly, status (with a long u) rather than the regular masculine plural in -i. I am not sure on what the OED editors based this pronouncement because there is in fact no evidence of the word being used in the plural in the original OED text. The revision to the Supplement to the OED, edited between 1972 and 1986, states "now usu. statuses" for the plural. I think they could have said "now always statuses". Nowhere in the whole text of the OED or the huge databases of quotations that we consulted for the dictionary was there any evidence for the plural "stati" (which, as we have seen, was not the Latin plural anyway) being used in the English language. It must be said also that "status" is simply not used much in the plural.
Despite my correspondent's categorical assertion, there are a number of other Latin borrowings in English ending in -us that form their plural with -es. For example:
and all the dinosaurs
When you get right down to it, even "bus" and "plus" are Latin words ending in -us, and yet no one says "Three bi drove past" (or writes to dictionary editors complaining that we should)!
There are many more such words where English speakers can choose between -es and -i but where -es is more common, such as thesaurus, focus, etc. (If you feel you "ought" to say "thesauri", get over it.)
English is English; Latin is Latin. Surprisingly, they are not the same language!