incidence

Usage Note: The singular noun incidence usually refers to the rate at which something happens, as in The city has taken measures to reduce the incidence of vandalism.In this sense, it is used in the plural only in relatively rare situations when several rates are being discussed (for example, incidences of heart disease, cancer, and stroke). However, incidence is often confused with the similar-sounding words incident and instance, which refer not to a rate but to a discrete event and are pluralized as incidents (which sounds exactly like incidence) and instances (which has an ending similar to incidences). This confusion often leads people to use incidences as a plural referring to a number of events, as in the sentence Incidences of religious intolerance are on the rise, creating tensions within many communities. In our 2014 Usage Survey, 74 percent of Panelists found this sentence unacceptable, and many Panelists remarked that incidences should be replaced with incidents or instances. The same sentence was unacceptable to 67 percent of Panelists in 2002, suggesting that there has been no increase in acceptability of this usage. A few Panelists remarked that this sentence might be acceptable if it were referring to rates of vandalism in several different places. A less ambiguous sentence (The election was marred by a few violent incidences) was rejected by 80 percent of the Panel. In this sentence, incidents is the better choice.