The verbs recur and reoccur (recurring and reoccurring in their present participle forms) both mean to “happen again” and can often be used interchangeably.
“Recur” is frequently the preferred choice in the context of regularly or periodically repeating events/occurrences (e.g., “This theme recurs throughout the book”).
If we’re describing something that happens again, but not regularly or periodically, then “reoccur” is often preferred (e.g., “This theme reoccurs in the second act of the play”).
You can use QuillBot’s free Grammar Checker to help you use “recur” and “reoccur” correctly in your writing.