Reoccurrence

Reoccurrence is the noun for the act of something occurring again after an initial occurrence. In many contexts it is used as a synonym of recurrence, but recurrence is the preferred form in formal writing. Some dictionaries recognize reoccurrence as a legitimate variant, while others mark it as less common and more prone to misspelling.

Usage distinctions exist between the two terms. Recurrence is often associated with cycles, repeating patterns, or medical relapses and is also a standard term in mathematics for a relation that defines later terms from earlier ones. Reoccurrence is broadly understood to mean the same idea, but may be chosen for emphasis or regional preference.

Common domains include medicine, where a patient may experience a reoccurrence of symptoms after treatment; meteorology, where similar weather events reoccur in a season; and daily language to describe repeated events. In mathematics and computer science, recurrence is the technical term for algorithms or sequences that repeat according to a defined rule.

Spelling guidance: for formal writing, prefer recurrence. Be aware of common misspellings such as reoccurence or reoccurrance. The related noun occurrence denotes something that happens, but not necessarily again.