The usual Standard words are recur, meaning “to return (to),” “to come back (to),” “to occur again,” as in The trouble recurred last week for the dozenth time; recurrence, meaning “one of several repetitions, yet another return,” as in If there’s another recurrence, we must take action; and the related adjective recurrent. Reoccur and reoccurrence are said to differ from recur and recurrence in that they suggest a first or single repetition: That odd noise reoccurred an hour later. They are rare in Edited English, and most desk dictionaries don’t include them, but they appear fairly often in the speech of the inexperienced as synonyms for recur and recurrence: That odd noise reoccurred just after you’d left. Its reoccurrence made me nervous. Especially in writing, best practical advice is to stick with recur and recurrence, for one repetition or many.
