I guess I’m on a language kick… After my recent post about the misuse of “similar to”, I’m going to tackle some Greco-latin plurals that lots of people don’t know how to use.

English is a lovely mongrel of a language, having adopted words and grammar from every invader who ever set foot on the island of Great Britain. The Romans ruled over England and Wales for about 350 years, so naturally, Latin left its mark on English. Some words were also adopted from Greek through the scholarly community. Most Latin and Greek words were eventually anglicized, and English-style pluralization rules applied, but a few retained their Greco-latin plurals. Some of these are heavily (mis)used in scientific writing. I’m going to try to sort out for you some of the ones that are most often used in the texts I read.

If you have a standard for judging something, you have a criterion. That’s right. Criterion. It’s possibly you have never seen this word and would have expected criteria instead, but criteria is the plural of criterion. It’s particularly important to get this right because English has just one definite article, “the”. Thus, “the selection criterion” and “the selection criteria” imply, respectively, one criterion and many. The meaning of the sentence is therefore altered if you use the wrong word. As another example, “a criteria”, which I see a lot, is wrong because “a” is a singular indefinite article, and “criteria” is plural. If you have one rule you use for making a decision, you have a criterion.

Erosion is a natural phenomenon. It’s one of the many geological phenomena that shape our Earth. So again, you would never write “a phenomena”.

Do you grow cells in a medium, or in a media? Hopefully, you would choose the singular “a medium“, media being the plural of medium. We might prepare media (if we are preparing several different media, or possibly several batches of a particular medium), but more commonly we might prepare a medium. It’s surprising how often media is used given how rarely it’s actually the syntactically and grammatically correct choice.

We can search for minima on a potential energy surface, on the assumption that there might be more than one, but when we find one, it’s a minimum. Obviously, the same comment would apply to maximum and its plural maxima, as well as optimum/optima. Incidentally, outside of science, people tend to say minimums and maximums for the plurals of these words—a usage that is sanctioned by modern dictionaries—so perhaps it’s time for us to stop trying to sound learned by using the Latin plurals. Errors in the singular would almost certainly vanish if we did so.

But please, no “criterions”, “phenomenons”, or “mediums”. Unless, in the latter case, you want to get together a group of people who can talk to the dead.