occurence

An occurrence is a single instance of something happening or being observed. It can refer to events in time or space, such as a weather occurrence, a fault, or a notable incident. In statistics and data analysis, occurrence denotes the presence or count of a particular event within a dataset, population, or sequence.

Origin and spelling: The noun derives from the verb occur, which comes from Latin occurre, meaning to meet or happen. The standard English spelling is occurrence. Occurence with a single r is a common misspelling.

Usage and related concepts: Occurrence is used to describe frequency or rate—for example, the occurrence rate of a disease. In linguistics and computing, it can refer to how often a word or a substring appears. In safety reporting, the term distinguishes actual events from their probability or risk, framing measurements as observed occurrences rather than hypothetical chances.

In scholarly writing, precision is important: authors distinguish the occurrence of an event from its probability or risk. The phrase number of occurrences is common when counting instances across a study period, a dataset, or an observed population.