Could someone please explain when to use incidents and when to use incidence? Thank you.

The words incidence and incident can be considered synonyms. Therefore, incidents can be substituted for incidences.

If I may, it's not so. They are not synonyms. An incident is an occurrence whereas incidence is the frequency of occurrence. Example: There were several traffic jam incidents that occurred over time vs. over time, the incidence of traffc jams increased.

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The words incidence and incident can be considered synonyms. Therefore, incidents can be substituted for incidences.