Uh-oh. He did something stupid again, and in public. Forget worrying about who exactly he is — is this yet another incident or incidence? These two related words can be confusing for many, and their similarities can make it easy even for copyeditors to miss.
Incidence is a mass noun that refers to the rate at which something happens. We talk about the incidence of crime or the incidence of a disease among a particular population, for example. An incidence is not (at least traditionally) a specific occurrence of something. For that, you want the related word incident.
An incident is a particular occurrence of something. It’s a count noun: If your tongue abruptly turns purple on Monday, that’s one incident. If, a week later, your tongue suddenly turns green, that’s two incidents. (It also means that your incidence of lingual discoloration doubled, from one incident to two.)
Incident normally carries a negative connotation — it’s the occurrence of something unpleasant or, as Merriam-Webster puts it, “an action likely to lead to grave consequences.” If, for example, your child’s principal calls you at home and begins the conversation with “There was an incident at school today,” she isn’t likely calling to tell you what wonderful thing your child did that day.
That incidence and incidents are homophones is, I believe, why the two are sometimes confused. Others might argue that we are actually seeing language change — that incidence is taking on the same sense as the singular incident in a natural and therefore acceptable way. I disagree, but even if it is true, this is a change I believe we copyeditors should push back against.
Conflating the two can lead to muddled meaning. To use a real-world example, consider this statement from a recent article at Forbes.com:
“Two-thirds of students worry about an incidence of gun violence on campus.”
- Does this mean that students are worried about how often there is gun violence on campus? Then it should read “…about the incidence of gun violence… “
- Does it mean the students are worried that someone will bring a gun on campus and use it? Then it should read either “…about an incident of gun violence…” or “…about incidents of gun violence…”
- Or the third option, which I hesitate to even include: Is this an intentional choice to use incidence to refer to an individual incident?
There’s one more sibilant word to throw into this mix: incidences.
Except as a synonym for incidents, incidence rarely needs to be made plural. (Compared to the other three related words, incidences barely even registers on the Google Ngram Viewer.) But there is room for it in our language for a very specific purpose: if we are comparing the occurrence rates of two different things. For example,
- the incidence of Type I and Type II diabetes
- the incidences of Type I and Type II diabetes
The former implies the rate of the two types of diabetes taken together — one number — and the latter of their rates separately — two numbers. However, because they are so similar, statements like these could stand to be clarified for the reader. Two possibilities:
- the combined incidence of Type I and Type II diabetes
- the incidence of Type I diabetes and of Type II diabetes
Incidence can be tricky, so pause to contemplate whenever you see it in your work. You just might lower your incidence of error.