Occurrences

An occurrence is an instance of something that happens or is observed. In everyday usage, it refers to a single event or an event that has been observed multiple times; counting occurrences helps quantify how common a phenomenon is. The term is often used for events that are irregular or noteworthy, such as unexpected occurrences, incidents, or episodes.

In probability, an occurrence is the realization of a random event. A probability space defines outcomes; when the outcomes corresponding to a specific event take place, the event occurs. The frequency of occurrences in a data sample is used as an empirical estimate of probability. For rare events, Poisson or binomial models are commonly applied.

In linguistics and corpus analysis, occurrences refer to word tokens in a text or corpus. The number and distribution of word occurrences underpin measures such as frequency, relative frequency, and term occurrence rate. These metrics support vocabulary studies, information retrieval, and stylometry.

In reporting and monitoring, occurrences are recorded as incidents or episodes. Accurate counting and consistent definitions are important for trends analysis, safety reporting, and epidemiology. The concept is widely applicable across disciplines wherever events are observed and counted.