The Grammarphobia Blog

The incident room

Q: A story on Accuweather.com the other day referred to more than 1,300 “incidences” of severe weather and damage. I sent the website a brief note that it should have been “incidents.” You may wish to address this on your site.

A: We think the confusion in using “incident” and “incidence” can be traced to two problems.

First, writers mix up “incidence” (singular) with “incidents” (plural) because they sound alike as spoken.

This is why journalists often put the wrong words into people’s mouths when quoting them, and consequently why the Internet is rife with misusages.

Second, people don’t understand the difference between the singulars, “incident” and “incidence.”

Both words entered English in the 15th century by way of French, but they’re ultimately derived from the Latin incidere (to fall into, fall upon, happen).

Over the years, the two words have shared several meanings, including the one in that weather story.

The adjective “incident,” also from the 15th century, is largely used today in technical and legal writing. For most of us, it may bring to mind a phrase familiar in crime fiction: “incident room.”

In modern usage, the nouns “incident” and “incidence” have different principal meanings, but the words overlap a lot, and seem to be growing more alike.

Let’s begin with their main senses in contemporary English.

An “incident” is a definite and separate occurrence—that is, an event of some kind, as in “I reported the incident to the police,” or “The commission reviewed three incidents of harassment.”

An “incidence” refers to the frequency or rate of an occurrence, as in “The incidence of measles has declined.”

The plural “incidences” is seen mostly in scientific writing, as in “This graph plots the incidences and risk factors for four diseases.”

However, “incidence” is often used to refer to an occurrence in a general way. An example in The American Heritage Dictionary of the English Language (4th ed.) refers to someone who “did not expect criticism and was surprised by its incidence.”

And an example in the Cambridge Dictionaries Online uses the word in the plural to mean separate occurrences: “There have been quite a few incidences of bullying in the school this year.”

Obviously, the difference between “incident” and “incidence” is fuzzy and getting fuzzier.

Nevertheless, we would use “incident” for a specific occurrence of something and “incidence” for the rate or frequency of an occurrence.

So if we were writing that Accuweather story, we’d refer to more than 1,300 “incidents” of severe weather and damage.

For anyone needing a good rule of thumb, Garner’s Modern American Usage (3rd ed.) has one:  “Wherever incidence appears where incident would fit, a switch is probably in order.”

Check out our books about the English language