English includes many nouns that end in “-um” or “-on” and are pluralized by changing the ending to “-a.” They come from Latin and Greek respectively. Examples include “medium,” “datum,” “ovum,” “criterion,” and “phenomenon.” As with everything else, the language isn’t consistent; we have museums, not musea; morons, not mora; polygons, not polyga. I wouldn’t complain if the language regularized the endings of all these words. “Bacteriums” and “phenomenons” would sound weird at first, but we could get used to it.

What’s happening instead is that people turn the plurals into singulars. With some words, like “data” and “media,” the change has been firmly established. Others are substandard but turn up often, like “a bacteria” or “a phenomena.” Recently I saw a writer friend who should know better talking about “a criteria.” This doesn’t make the words any more regular, since double-pluralizing “medias” or “datas” is still frowned upon. It leaves us with words that are the same in the singular and the plural.

People think that anything that doesn’t end in “-s” can’t be a plural, or something like that, yet we have “mice,” “sheep,” “fish,” and other plurals that don’t end in “-s.” We use these words a lot more than “phenomenon” or “bacterium,” so they’re less prone to change. “Data” became a singular word in a time when it was less used than today.

Occasionally there are “-a” plurals that have no singular. One non-canonical book of the Bible should be an “apocryphon,” but does anyone use that word? The word “candelabrum” for a single candlestick actually exists, though I hadn’t heard of it before I researched this article.

Personally, I think the people who singularize these plurals should be treated as linguistic hoodla and forced to listen to badly played accordia while not being allowed to drink even one Coca-Colon.